ELEMENTARY 
LESSON  SIN  PHYSICS  I 


BY 
J.B.GIFFORD 


THOMPSON, 

BROWN   &  CO, 


Southern  Branch 
of  the 

University  of  California 


Los  Angeles 


Form  L  1 


QC 

33 


This  book  is  DUE  on  the  last  date  stamped  below 

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ELEMENTARY    LESSONS 


IN  PHYSICS. 


JOHN   B.  GTFFORD, 

SCPEKINTENDENI  OF  SCHOOLS.  FKABOUV,  MASS. 


THOMPSON,  BROWN,  AND    COMPANY. 
BOSTON.  CHICAGO. 


Copyright,  1894- 
BY  JOHN  B.   GIFFORD. 


JOHN  WILSON  AND  SON,  CAMBRIDGE.  U.S. A. 


3 


G  36 


PEEFACE. 


THE  following  Lessons  have  been  growing  into  their 
present  form  for  several  years,  during  which  time  they 
have  been  used  in  classes  under  the  supervision  of  the 
author.  Within  the  past  year  they  have  been  revised,  with 
the  aim  of  adapting  them  to  general  use. 

It  is  confidently  hoped  that  these  Lessons  will  meet  a 
want  which  is  being  increasingly  felt  by  teachers  and 
school  officers  for  a  suitable  text-book  to  aid  them  in 
training  the  pupils  of  the  upper  grammar  and  lower  high 
school  grades  to  observe,  to  think,  and  to  express  thought, 
and  in  revealing  to  them  some  of  the  laws  in  accordance 
with  which  physical  changes  occur. 

It  has  been  the  author's  aim  to  guide  the  investigations 
of  the  learner  by  directions  and  questions  so  definite  that 
he  will  generally  be  able  to  get  the  points  desired  without 
aid.  Occasionally  a  question  is  asked  which  only  a  small 
proportion  of  the  class  may  be  able  to  answer ;  but  the 
question  should  at  least  secure  the  attention  of  all,  and 
prepare  them  to  grasp  the  truth  when  it  comes ;  and  the 
closer  workers  will  get  the  exercise  which  they  need. 


vi  PREFACE. 

The  illustrations  have  been  introduced  to  show  the  con- 
ditions of  the  experiments,  and  not  the  results. 

Messrs.  Frank  L.  Keith,  J.  M.  Dill,  and  Charles  F.  King, 
of  Boston,  Mr.  Clarence  Boylston,  of  Milton,  Mass.,  and 
Mr.  Preston  Smith,  instructor  in  Physics,  Brockton,  Mass., 
have  kindly  read  through  these  Lessons  in  manuscript  or 
in  proof,  and  suggested  many  valuable  improvements. 

Whatever  of  merit  there  may  be  in  the  aim  and  general 
plan  of  the  work  should  be  largely  credited  to  my  esteemed 
teacher  in  Physics,  Mr.  George  H.  Martin,  of  Boston. 

JOHN  B.   GIFFORD. 
JUNE,  1894. 


CONTENTS. 


Topics  marked  (t)  are  suggested  for  the  earlier  study,  in  schools  in  which  this  work  is 
not  confined  to  a  single  year. 

Those  marked  (*)  are  suggested  for  the  later  study,  where  the  work  is  distributed  through 
two  or  more  years. 


PAGE 

I.    NATURE  OF  MATTER 1 

Matter,  Body,  Substance,  Impenetrability. 

II.    DIVISIONS  OF  MATTER 5 

Molecule,  Mass,  Atom. 

III.  STATES  OF  MATTER  f 8 

Liquids,  Solids,  Aeriform  Matter. 

IV.  CHANGES  IN  MATTER 14 

Chemical  Change,  Physical  Change. 

V.    FORCE 16 

Definition,  Physical  and  Chemical,  Muscular  Force,  Grav- 
itation, Gravity,]  Cohesion,  Adhesion,  Heal,  Light, 
Magnetism,  Fractional  Electricity,  Voltaic  Electricity, 
Correlation  of  Forces,  Molecular  Attraction,  Molar 
Force,  Momentum,  Inertia,  Work,*  Power,*  Energy,* 
Composition  of  Forces* 

VI.    GRAVITY 45 

Centre  of  Gravity.*  Line  of  Direction,*  Equilibrium,* 
Falling  Bodies,*  Pendulum,*  Pressure  of  Liquids,] 
Water  Works  for  Cities  and  Towns,  Spirit  Level, 
Springs  and  Wells,]  Artesian  Wells,  Floating  and 
Sinking,  Specific  Gravity,*  Pressure  of  Air,  Barometer, 


vjii  CONTENTS. 

PA« 
VII.    SIMPLE  MACHINES* 71 

Lever,  Wheel  and  Axle,  Pulley,  Inclined  Plane,  Screw, 
Wedge. 

VIII     HEAT 87 

Sources  of  Heat,  Effects  of  Heat,]    Transfer  of  Heat, 

Latent  Heat.* 

IX.    MAGNETISM 103 

Magnets,  Terrestrial  Magnetism. 

X.    FRICTIONAL  OR  STATIC  ELECTRICITY* 107 

How  Excited,  Electroscopes,  Kinds  of  Electricity,  Law, 
Conduction,  Induction. 

XI.    VOLTAIC  ELECTRICITY* 114 

Voltaic  Element,  How  Produced,  Effects. 

XII.    SOUND     .     . 117 

How  Produced,  Transmission  of  Vibrations,  Vibrating 
Strings,  Vibrating  Columns  of  A  ir.* 

XIII.  LIGHT 126 

Sources,  Porte  Lumiere,  Direct  Transmission,]  Shadows,] 
Reflection*  Refraction*  Microscopes,*  Refracting  Tel- 
escope,* Solar  Spectrum 

XIV.  CHEMISTRY  OF  AIR  AND  WATER* 145 

Composition  of  the  Air,  Properties  of  Oxygen,  Combustion, 
Composition  of  Water,  Changes  in  the  Human  Body. 


SUGGESTIONS  TO  TEACHERS. 


PUPILS  may  perform  at  home  such  of  the  experiments  as 
do  not,  call  for  special  apparatus.  Each  teacher  must  decide 
for  himself  whether  this  plan  is  the  most  satisfactory  for  his 
class. 

Wherever  the  experiments  are  performed,  each  pupil  should 
observe  and  infer  for  himself,  and  commit  to  writing  the  results 
of  his  work  before  they  are  reported  in  the  class  exercises. 

These  records  may  be  made  upon  separate  sheets  of  paper 
of  uniform  size,  each  statement  marked  to  correspond  with  the 
directions  in  the  manual.  If  only  one  observation  is  called  for 
under  an  experiment,  it  is  marked  Obs.  ;  if  more  than  one,  they 
are  numbered  Obs.  1,  Obs.  2,  etc.  In  the  same  way  inferences 
are  marked,  —  Inf.,  or  Inf.  1,  Inf.  2,  etc.  Other  facts  to  be 
recorded  under  each  experiment  are  usually  numbered. 

After  these  results  have  been  reported  and  compared  in  the 
recitation,  and  opportunity  given  for  correcting  errors,  by  re- 
peating experiments,  it  would  seem  well  that  they  should  be 
neatly  recorded  in  note-books. 

This  material  should  form  the  basis  of  much  written  language 
work,  in  which  the  pupil  should  develop  the  subject  assigned 
by  complete  descriptions  of  experiments,  with  drawings  of  the 
apparatus  used. 

For  the  derivation  of  terms,  suggested  as  profitable  language 
study,  a  list  of  the  required  prefixes  and  suffixes,  with  their 
meanings,  will  be  found  on  page  157. 

The  work  laid  out  in  these  Lessons  may  all  be  done  with  a 
class  in  a  single  year ;  but  some  will  prefer  to  distribute  it  over 
a  longer  period,  and  the  derivation  of  terms  and  many  of  the 
general  topics  may  be  omitted  without  hindering  the  study  of 
the  others. 


ELEMENTARY  LESSONS  IN  PHYSICS. 

v-V  " .     "  f 

I    NATURE  OF  MATTER. 
MATTER,    IMPENETRABILITY. 


OBSERVATION,   DERIVATION,  INFERENCE. 

EXPERIMENT  1.    (To  be  performed  at  home.) 

FILL  a  bottle  with  water,  and  insert  your  pencil 
Observation.     State  what  the  water  does. 

(In  NOTE-BOOK.*)  Experiment  1.   Obs.   Qrome  o/  tine 


Inference.     What  causes  it  to  do  this  ? 
(NOTE-BOOK.)     Inf.     1.    Q%e   /o#£  wa<t  ^a//  o 

ana  tn^eze  wa<t  no  loom  #01  trie  faencii.        &fo  tvnen   tne 
/  / 

/lencii  wa&  intezted  tome  o/  tne  watez  mu<tt  come  oat. 
<  / 

1.    How  did  you  learn  what  the  water  did  ? 
(NOTE-BOOK.)     1.  Q?  <taw  it  tun  ovev. 
Call  a  fact  learned   through  the  senses  an  obser- 
vation. 

*  See  preface  for  suggestions  in  regard  to  records  in  Note-book. 


2  ELEMENTARY  LESSONS  IN  PHYSICS. 

In  the  dictionary  you  will  find  observe  given  as  formed  from  the 
Latin  observare,  meaning  to  pay  attention  to,  to  watch.  After  this  is 
placed  the  suffix  turn,  meaning  the  act  of. 

Inf.  2.  What  is  the  meaning  of  the  whole  word  as  you  get  it  from 
its  formation  ? 

(NOTE-BOOK.)  Inf.  2.  QPvom  t/ie  meaning  of  M* 
hazta.  it  wouJa'  mean  t^e  act  o/  fraying,  attention  to, 


2.   Can  you  see  any  connection  between  this  meaning  and  the  sense 
in  which  we  have  used  it  above  ? 


(NOTE-BOOK.)     2.    Q/ne    tact   teazned  M    tne 

hauina    attention, 
ff     ff 

This  tracing  out  the  origin  of  words  is  called  derivation. 

In  this  work  always  try  to  discover  the  connection  between  the  origi- 
nal meaning  of  the  word  and  the  sense  in  which  you  find  it  used. 

3.    How  did  you  learn  what  caused  the  water  to 
run  over  in  the  above  experiment  ? 

(NOTE-BOOK.)     3.  Q/   wazned  it  6-u  tninnina. 

Call  a  fact  obtained  by  thinking,  or  reasoning  from 
other  facts,  an  inference. 

Give  the  derivation  of  this  word. 
(NOTE-BOOK.) 


m&we,  meanina  to  ozina  fo^^(^a^a/,  and  tne  <M/$&  ence, 

,     ff ff  <7     ff  ffff  

meanina  me  aaa/itu  o/,  tne  act  o/,  and  dometimed    tae 
teau/t  o/,  oz  tnat  wnicn.         (JTLete   tae  <ten*e  Aeem*   to   rfe 

ft'    fl         *  fl  fl  ^  /        fl  ft  •        ^' 

wntcn<    14    vwaafist    /otwata    vu    tfibnfiina. 


NATURE   OF  MATTER. 


EXPERIMENT  8.     (At  home.) 


Holding  an  inverted  tumbler  evenly  above  a  basin 
of  water,  push  it  downward  into  the  water. 


Obs.   Observe  the  height  of  the  water  under  the 
tumbler. 

Inf.  1.   What  keeps  it  from  rising  higher? 
Inf.  2.    Why  does  that  prevent  it  from  rising  ? 

1.  Name  three  other  things  that  take  up  room. 

2.  Does  a  thought  take  up  room  ? 

3.  Can  you  think  of  other  things  which  do  not  ? 
Call  that  which  occupies  room  matter. 

BODY. 

4.  Name  six  different  pieces  of  matter. 
Call  them  bodies. 

5.  What,  then,  is  a  body  ? 


4  ELEMENTARY  LESSONS  IN   PHYSICS. 

SUBSTANCE. 

6.  Name  six  different  kinds  of  matter. 
Call  each  kind  of  matter  a  substance. 

7.  What  is  a  substance  ? 

Derive  substance. 

Inf.  3.  How  many  bodies  can  occupy  the  same 
space  at  the  same  time  ? 

Call  the  property  of  matter  by  which  no  two  bodies 
can  occupy  the  same  space  at  the  same  time  impenetra- 


Define  impenetrability. 

Derive  the  term. 


-L'CilVC    LUG    tCJ  111. 

Describe  experiments  showing  the  impenetrability 

YYlQ-f  -f  £i1» 


of  matter. 


DIVISIONS  OF  MATTER.  5 

H    DIVISIONS   OF  MATTER. 
MOLECULE,  MASS. 

EXPERIMENT  3.     (At  home.) 

Break  a  lump  of  salt  into  several  pieces. 

Dry  one  small  piece  thoroughly,  and  powder  as  fine 
as  possible  in  a  mortar. 

Notice  the  size  of  these  particles. 

Imagine  the  division  to  be  continued  until  the 
smallest  particles  which  can  exist  by  themselves  have 
been  formed. 

Call  these  molecules. 

Thus,  the  smallest  particles  of  any  substance  which 
can  exist  by  themselves  are  called  molecules. 

Derive  molecule. 

Call  any  quantity  of  matter  greater  than  a  molecule 
a  mass. 

Derive  mass. 

1.   Name  six  masses  of  matter. 

COMPOUND. 

Each  of  these  molecules  of  salt  is  composed  of  the 
metal  sodium  and  a  green  gas  called  chlorine. 

Let  the  teacher  show  a  piece  of  sodium,  and  prepare  a  little  chlo- 
rine by  adding  sulphuric  acid  to  a  little  bleaching  powder  in  a  test 
tube  or  large-mouthed  bottle. 

Be  careful  not  to  inhale  much  of  the  chlorine.  Sodium  should  be 
handled  with  forceps  or  dry  paper,  and  kept  under  petroleum  or 


6  ELEMENTARY  LESSONS  IN   PHYSICS. 

-06s.    Describe  sodium  and  chlorine. 

Sodium  and  chlorine  are  always  combined  in  exactly 
the  same  proportion  to  form  salt. 

Call  a  substance  which,  like  salt,  has  been  found  to 
be  composed  of  two  or  more  different  kinds  of  matter 
combined  in  definite  proportions  a  compound. 

Water,  alcohol,  acids,  kerosene,  and  iron-rust  are 
compounds. 

2.  Compounds  are  what  kind  of  substances  ? 

Derive  the  term. 

ELEMENT. 

Sodium   has   never   been    separated   into   different 
kinds  of  matter.     Neither  has  chlorine. 
Call  such  substances  elements. 

3.  What  do  you  understand  by  "  such  substances  "  ? 
Oxygen,  hydrogen,  nitrogen,  carbon,  iron,  lead,  tin, 

gold,  and  silver  are  some  of  the  common  elements. 

Derive  element. 

ATOMS. 

4.  A  molecule  of  salt  contains  what  elements  ? 

Inf.  How  must  the  quantity  of  sodium  in  a  mole- 
cule compare  with  the  quantity  of  salt  in  the  mole- 
cule? 

Call  the  smallest  particle  of  matter  which  can  exist 
combined  with  other  particles  an  atom. 

5.  What  is  an  atom  ? 

Derive  the  term. 


DIVISIONS  OF  MATTER.  7 

6.  Name  the  divisions  of  matter  which  we  have 

considered. 

7.  Which  of  these  have  you  seen  ? 
Inf.  2.   Do  the  others  really  exist  ? 


SIZE  OF  MOLECULES. 

EXPERIMENT  4.    (At  home.) 

Add  a  drop  of  "  bluing     to  a  tumbler  of  water. 

Obs.    State  the  effect. 

Inf.  1.    What  gives  the  color  to  the  "  bluing"  ? 

Inf.  2.    What  to  the  water  in  the  tumbler  ? 

Inf.  3.    Where  are  these  particles  ? 

Inf.  4.  What  do  you  infer  in  regard  to  the  size  of 
the  molecules  of  coloring  matter? 

The  odor  of  a  substance  is  supposed  to  be  due  to 
small  particles  of  the  substance  floating  in  the  air  and 
coining  in  contact  with  the  nerve  of  smell.  A  little 
sachet  powder  will  fill  the  air  with  perfume  for  a  long 
time  without  undergoing  any  sensible  loss  of  weight. 

Inf.  5.  What  do  you  infer  from  this  in  regard  to 
the  size  of  the  molecules  ? 


g  ELEMENTARY  LESSONS  IN   PHYSICS. 

HI.    STATES  OF  MATTER. 

1.  LIQUIDS. 

EXPERIMENT  5.    (At  home.) 

Put  your  finger  into  water,  and  stir  it  round. 

Obs.  1.  Observe  the  ease  with  which  the  finger 
is  moved  through  the  water. 

Inf.  I.  Make  an  inference  in  regard  to  the  move- 
ment of  the  particles  of  water  among  themselves. 

Remove  your  finger,  keeping  the  end  downward. 

Obs.  2.    Observe  what  forms  at  the  end. 

Inf.  2.  Infer  whether  the  particles  tend  to  separate 
or  to  cling  together. 

1.  What  two  things  do  you  find  to  be  true  of  the 

particles  of  water  ? 

2.  Name  three  other  substances  of  which  the  same 

is  true. 

3.  What  common  name  may   you  give   to   these 

substances  ? 

4.  What  would  you  say  that  liquids  are?      (See 

question  1,  above.) 

Derive  liquid. 

2.  SOLIDS. 

5.  Compare  wood,  iron,  and  glass  with  liquids. 

In  which  of  the  above  points  do  they  agree  ? 

(See  question  1.) 
In  which  do  they  differ  ? 


STATES   OF   MATTER. 


EXPERIMENT  6.     (At  school.) 


Fasten  one  end  of  a  stick  of  sealing  wax  firmly  in  a 
horizontal  position.  Leaving  the  other  end  unsup- 
ported, suspend  from  it  a  weight  of  one  quarter  of  a 
pound. 


Fig.  2. 

Obs.  Let  it  remain  for  two  days,  observing  the 
effect  from  time  to  time. 

What  is  the  result  ? 

Inf.  1.  Make  an  inference  in  regard  to  the  move- 
ment of  the  molecules  among-  themselves. 

Inf.  2.  Give  a  common  name  for  such  substances 
as  wood,  iron,  and  wax. 

What  have  you  found  to  be  the  distinguishing 
properties  of  these  substances?  (See  question  5, 
above,  and  Inf.  1.) 

How  would   you  define  solids. 

Derive  the  term. 


10  ELEMENTARY   LESSONS   IN   PHYSICS. 


3.     AEEIFOKM  MATTER 

EXPERIMENT   7.     (At  school.) 

Fit  two  horse-radish  bottles  with  air-tight  cork 
stoppers. 

Half  fill  one  bottle  with  water. 

Cut  off  two  pieces  of  glass  tubing  an  inch  longer 
than  the  height  of  the  bottles,  and  one  piece  about 
two  inches  long. 

To  cut  glass  tubing  make  a  nQtch  on  one  side  by  two  or  three  for- 
ward strokes  of  a  triangular  file,  grasp  the  tube  in  both  hands  with  the 
thumbs  against  it  opposite,  on  the  other  side  from  the  notch,  and 
break  by  pressing  out  with  the  thumbs  and  drawing  towards  you  with 
the  outsides'of  the  hands.  Heat  the  ends  of  the  pieces  of  tubing  in  the 
gas  or  alcohol  flame  until  the  sharp  edges  are  rounded. 


Fig.  3. 


With  a  rat-tail  file  bore  a  hole  in  the  stopper  of  the 
bottle  containing  the  water,  just  large  enough  for  the 
tube  to  fit  air-tight ;  and  push  one  of  the  longer  tubes 
through  the  hole  so  that  it  will  reach  nearly  to  the 
bottom  of  the  bottle. 


STATES   OF   MATTER. 


11 


In  the  same  way  fit  the  other  two  tubes  into  the 
stopper  of  the  other  bottle,  letting  them  project  about 
a  quarter  of  an  inch  below  the  stopper. 

Connect  the  two  bottles  by  a  piece  of  rubber  tubing 
drawn  over  the  ends  of  the  glass  tubes  which  project 
but  little  above  the  stoppers. 


Fig.  4. 

Obs.  1.   What  is  in  the  bottles  now  ? 

Taking  the  end  of  the  projecting  tube  in  the  mouth, 
"  draw  out "  as  much  air  as  you  can. 

Obs.  2.    What  is  the  effect  ? 

Inf.  1.    Infer  the  cause  of  this. 

Inf.  2.  What  tendency  of  the  molecules  of  air  is 
shown  in  this  experiment  ? 

1.  How  does  air  differ  from  liquids  ? 

2.  In  what  respect  is  it  like  liquids  ? 

Call  such  matter  as  air  aeriform  matter. 

3.  What  are  its  distinguishing    properties?      (See 

questions  1  and  2.) 


12  ELEMENTARY  LESSONS   IN   PHYSICS. 

4.  Define  aeriform  matter. 

Derive  aeriform. 

5.  What  other  aeriform  matter  have  you  seen  ? 

6.  What  name  is  applied  to  both  liquids,  and  aeri- 

form matter  ? 


GAS  AND   VAPOR. 

EXPERIMENT  8.     (At  school.) 

Boil  a  little  water  in  a  test  tube. 

Obs.    Notice  what  is  formed,  and  where  it  goes. 

Inf.  1.    What  is  it  formed  from  ? 


Fig.  5. 


STATES  OF  MATTER.  13 

Inf.  2.   When  wet  clothing  dries  where  does  the 
water  go? 

1.  Can  you  see  this  water  in  the  air  ? 

2.  In  what  state  of  matter  is  water  ordinarily  ? 

3.  In  what  state  of  matter  is  this  invisible  water 

in  the  air  ? 
Call  such  aeriform  matter  vapor. 

4.  How  does  it  differ  from  air  ?     (See  question  2.) 
Call  such  aeriform  matter  as  air  gas. 

5.  What  other  gases  have  you  known  ? 

Write  a  connected  description  of  the  different  states 
of  matter,  showing  by  illustrations  what  each  is. 


14  ELEMENTARY  LESSONS   IN   PHYSICS. 


IV.    CHANGES  IN  MATTER. 
1.    CHEMICAL  CHANGE. 

EXPERIMENT  9.    (At  school.) 

Place  a  little  copper  in  a  test  tube. 
Add  about  twice  its  weight  of  nitric  acid. 
Obs.     Observe,  and  state  the  effect  in  the  liquid, 
and  above  the  liquid. 

Inf.  1.    Infer  what  gives  the  color  to  the  liquid. 

Would  copper  give  it  that  color?     Would  nitric  acid? 

Inf.  2.  How  many  new  substances  are  being  formed 
in  the  liquid  ? 

1.  How  does  each  differ  from  copper  ? 

2.  How  does  each  differ  from  nitric  acid  ? 
Inf.  3.    What  are  they  formed  from  ? 
Why  do  you  think  so  ? 

Inf.  4.  Are  the  molecules  of  these  new  substances 
the  same  as  those  of  the  copper  and  nitric  acid  ? 

3.  Why  do  you  think  so  ? 

Inf.  5.  .Are  the  atoms  the  same  ? 

Call  a  change  in  which  the  atoms  of  one  or  more 
substances  combine  in  such  a  way  as  to  form  one  or 
more  new  substances  a  chemical  change. 

Derive  the  term  chemical. 

Inf.  6.    In  the  preceding  experiment  were  the  cop- 
per and  nitric  acid  changed  into  nothing  ? 
Inf.  7.    What  became  of  them  ? 

4.  What  other  chemical  changes  have  you  seen  ? 


CHANGES  IN  MATTER.  15 

2.   PHYSICAL  CHANGE. 

1.  Were  any  new  substances  formed  in  the  first 

experiment  ? 

2.  How  does  the  ninth  differ  from  this  ? 

Call  a  change  in  matter  in  which  no  new  sub- 
stance is  formed  a  physical  change. 

3.  What  kinds  of  changes  have  occurred  in  each 

of  the  other  experiments  performed  ? 

PHYSICS. 
Call  the  knowledge  of  physical  changes  Physics. 

Derive  the  terms  physics  and  physical. 

Call  the  knowledge  of  chemical  changes 

Write  a  connected   description  of  the  changes  in 
matter,  illustrating  by  experiments. 


16  ELEMENTARY  LESSONS  IN  PHYSICS. 

V.    FORCE. 
1.   DEFINITION. 

Call  that  which  produces,  or  tends  to  produce, 
change  force. 

As  to  what  this  cause  of  cnange  really  is,  we  know  nothing.     We 
must  infer  that  there  is  a  cause,  and  we  name  it  force. 
Derive  the  word  force. 

2.  PHYSICAL  AND   CHEMICAL. 

Inf.  1.  The  cause  of  a  physical  change  would  be 
called  what  kind  of  a  force  ? 

Inf.  2.  The  cause  of  a  chemical  change  would  be 
called  what  kind  of  a  force  ? 

It  is  also  called  chemical  affinity. 

Derive  affinity. 

1.  It  acts  between  what  divisions  of  matter  ? 

2.  Physical  forces  act  between  what  divisions  of 

matter  ? 

3.  DIFFERENT   FOECES. 
a.  MUSCULAR  FORCE. 

EXPERIMENT   1O.     (At  home.) 

Lift  a  chair,  and  hold  it  at  arm's  length. 
Inf.  1.    What  produces  this  change  ? 

1.  By  what  was  the  force  exerted  ? 

Inf.  2.   Infer  a  name  for  force  so  exerted. 

2,  Give  other  illustrations  of  the  use  of  such  force. 


FORCE.  17 

&    GRAVITATION. 

EXPERIMENT   11.      (At  home.) 

Fill  a  wooden  pail  with  water. 

When  the  water  has  come  to  rest  scatter  a  few 
blocks  or  chips  of  wood  over  its  surface. 

Obs.  1.  Observe  any  change  in  the  positions  of  the 
blocks. 

Obs.  2.  Let  the  pail  stand  for  an  hour,  and  observe 
the  positions  in  which  the  blocks  have  come  to  rest. 

Inf.    Infer  the  cause  of  the  change. 

Where  have  you  noticed  similar  results  ? 

EXPERIMENT  12.     (At  home.) 

Hold  a  brick,  or  a  stone  as  large  as  a  brick,  two  or 
three  feet  from  the  ground,  and  let  go. 
Obs.   State  what  happens. 
Inf.    Infer  the  cause. 

EXPERIMENT  13.     (At  home.) 

Place  a  brick  upon  the  hand. 
Obs.  1.    Observe  the  effect. 
Inf.  1.    Infer  the  cause. 

1.  Upon  what  divisions  of  matter  did  the  force  mani- 

fested in  the  last  three  experiments  act  ? 

2.  In  what  directions  with  reference  to  each  other 

did  it  draw  the  bodies  ? 
Call  this  force  gravitation. 

3.  What,  then,  would  you  say  that  gravitation  is  ? 

Derive  gravitation. 


18  ELEMENTARY  LESSONS  IN  PHYSICS. 


GRAVITY. 

4.  In  the  last  two  experiments  gravitation   acted 

between  what  two  bodies  ? 

5.  Between  the  earth  and  what  other  bodies  have 

you  found  that  this  force  acts  ? 
Call  the  attraction  between  the  earth  and  bodies  on 
or  near  its  surface  gravity. 

Derive  the  term. 

6.  What  other  name  applies  to  this  force?     (See 

question  2.) 

7.  Which  is  the  more  definite  name  ?     Why  ? 

Inf.  2.  Infer  another  name  for  a  force  which  draws 
together. 

Since  it  draws  masses  together  it  is  called  molar 
attraction. 

Derive  these  words. 

Obs.  2.  If  you  fasten  a  string  to  a  horse-chestnut 
and  swing  it  so  that  it  moves  in  the  circumference  of 
a  circle,  what  is  the  effect  upon  the  fingers  ? 

Obs.  3.    If  you  let  go  the  string,  what  happens  ? 

Inf.  3.  This  shows  that  a  body  moving  in  the 
circumference  of  a  circle  tends  to  move  in  what  kind 
of  a  line  ? 

8.  What  other  evidence  of  this  tendency  have  you 

noticed  ? 
This  tendency  has  been  called  centrifugal  force. 

9.  Describe  the  tendency. 

Derive  centrifugal. 


FORCE.  19 

The  earth  and  other  planets  move  round  the  sun  in 

nearly  circular  orbits. 

Inf.  4.    What  prevents  them  from  moving  off  in 
straight  lines  ? 

c.  COHESION. 

Inf.  5.    What  would  you  call  that  which  holds  the 
molecules  of  a  substance  together  ?     (See  Inf.  2.) 
10.    This  force  acts  between  molecules  of  the  same 
kind,  or  of  different  kinds  ? 

Call  the  force  which 

together  cohesion. 

Derive  the  word. 

d.  ADHESION. 

EXPERIMENT   14.    (At  home.) 

Insert  your  pencil  in  water,  and  withdraw  it. 
Obs.    Observe  the  effect  upon  the  pencil. 
Inf.    Infer  the  cause. 

EXPERIMENT   15.    (At  home.) 

Rub  the  lead  of  your  pencil  across  a  piece  of  paper. 
Obs.   Observe  the  effect  upon  the  paper. 
Inf.   Infer  what  causes  this. 

1.  Are  the  molecules  of  lead  and  paper  alike  ? 
Call  the  force  which  holds  molecules  of  different 

substances -together  adhesion. 

Derive  adhesion. 

2.  How  does  it  differ  from  cohesion  ? 

3.  In  what  do  cohesion  and  adhesion  agree  ? 
Hence  the  term  molecular  attraction  is  applied 

to  both. 


20  ELEMENTARY  LESSONS  IN  PHYSICS. 

e.   HEAT. 

EXPERIMENT   16.    (At  home.) 

Hold  a  piece  of  wax  near  the  flame  of  a  burning 
match. 

Obs.    Observe  the  effect  upon  the  wax.' 

Call  the  force  which  causes  this  change  heat. 

f.  LIGHT. 

EXPERIMENT   17.    (At  school.) 

Moisten  a  strip  of  paper  four  inches  long  in  a 
solution  of  silver  nitrate. 

Shut  one  half  of  the  paper  between  the  leaves  of  a 
book,  and  leave  the  other  half  exposed. 


Fig.  6. 


Place  the  book  where  the  sun  will  shine  upon  the 
exposed  half  of  the  paper,  and  leave  it  there  for  ten 
minutes. 

06s.    Observe  the  effect  upon  each  half  of  the  paper. 

Inf.   Infer  what  force  produced  the  change. 


FORCE.  21 

y.  MAGNETISM. 

EXPERIMENT  18.    (At  schooL) 

Obs.  Bring  a  magnet  near  to,  or  in  contact  with, 
pieces  of  copper,  iron,  zinc,  lead,  silver,  steel,  wood, 
and  other  substances,  and  observe  the  effect. 

Inf.    Infer  what  must  have  produced  this  effect. 

Call  this  force  magnetism. 

Derive  magnet  and  magnetism. 

h.  FRICTIONAL  ELECTRICITY. 

EXPERIMENT  19.    (At  home.) 

Fold  a  piece  of  silk  cloth  into  a  pad  five  or  six 
inches  square. 

Warm  the  pad,  and  also  a  straight  lamp  chimney 
or  stick  of  sealing  wax. 

Obs.  1.  Bring  them  successively  near  some  small 
bits  of  paper,  and  see  if  they  affect  the  paper. 

Rub  the  chimney  briskly  with  the  silk,  and  repeat 
the  experiment. 

Obs.  2.    State  the  effect. 

Inf.  1.    Infer  the  cause. 

Inf.  2.    Infer  how  this  force  was  produced. 

Call  it  f notional  electricity. 

Derive  these  words. 

».  VOLTAIC  ELECTRICITY. 

EXPERIMENT  2O.     (At  school.) 

Into  a  tumbler  two  thirds  full  of  water  pour  about 
one  twelfth  as  much  sulphuric  acid. 


22  ELEMENTARY  LESSONS  IN  PHYSICS. 

Add  as  much  potassium  bichromate  as  will  dissolve. 

In  this  solution  insert  a  plate  of  sheet  copper  and 
one  of  sheet  zinc,  each  about  2x5  inches. 

Obs.  1.  Holding  them  so  that  they  will  not  touch 
each  other,  observe  the  surfaces  of  the  metals. 

Obs.  2.  Touch  their  outer  ends  together,  and  ob- 
serve any  action  upon  the  surface  of  either  or  both. 

Inf.  1.   What  kind  of  change  is  this  ? 

Remove  the  plates,  punch  a  hole  near  the  top  of 
each,  and  connect  them  by  a  piece  of  copper  wire  16 
inches  long,  as  shown  in  Figure  7. 


Fig.  7. 


Obs.  3.  Insert  the  plates  in  the  solution,  and  see  if 
there  is  any  action  upon  the  surface  of  either. 

Remove  the  plates. 

Magnetize  a  large  needle  or  half  a  knitting  needle, 
by  rubbing  the  end  of  a  magnet  from  one  end  of  the 
needle  to  the  other,  always  in  the  same  direction. 


FORCE.  28 

Suspend  this  needle  by  a  silk  thread  so  that  it  will 
balance  in  a  horizontal  position. 

When  the  needle  has  come  to  rest  hold  the  wire 
connecting  the  plates  parallel  with  the  needle  and 
just  below  it ;  and  then  just  above  it. 


Fig.  8. 

Obs.  4.   Was  the  needle  affected  ? 

Insert  the  plates  in  the  liquid  in  the  tumbler,  and 
hold  the  wire  to  the  needle  as  before. 

Obs.  5.   State  the  effect. 

Call  the  force  which  produces  this  change  voltaic 
electricity. 


24  ELEMENTARY  LESSONS  IN  PHYSICS. 

Inf.  2.    How  was  it  developed?     (See  Inf.  1.) 

Derive  the  term  voltaic. 

1.  Name  the  different  forces  which  we  have  been 

considering. 

2.  Which  of  these  act  upon  masses  ? 

Inf.  3.    What  kind  of  forces  may  you  call  them  ? 

3.  Which  act  upon  molecules  ? 

Inf.  4.   What  kind  of  forces  may  they  be  called  ? 

4.  Which  tend  to  bring  bodies  together  ? 
Gravitation  has  also  been  called  molar  attraction. 

5.  Which  of  these  forces  hold  molecules  together  ? 

6.  What  common  name  have  you  given  to  these 

forces  ? 

Write  a  connected  description  of  the  different  forces 
studied,  illustrating  them  by  experiments. 

4.    CORRELATION   OF   FORCES. 

EXPERIMENT  81.    (At  home.) 

Touch  a  cent  to  your  cheek. 

Rub  one  side  of  it  briskly  against  your  sleeve  for  a 
few  seconds,  and  touch  it  to  the  cheek  again. 
06s.   Observe  any  change. 
Inf.   Infer  how  it  was  produced. 

1.  What  force  was  applied  in  the  experiment  ? 

2.  What  force  was  developed  by  it  ? 

3.  In  what  other  cases  have  you  noticed  that  heat 

was  developed  by  friction  ? 


FORCE.  25 


EXPERIMENT  82.    (At  home.) 

05s.  1.  Examine  a  common  match  and  see  what  it 
consists  of. 

The  substance  with  which  the  tip  is  coated  is  a 
preparation  containing  phosphorus. 

Rub  the  end  of  the  match  over  a  rather  rough 
surface. 

Obs.  2.    Observe  and  state  carefully  what  happens. 

Note  the  color  of  the  flame,  and  any  change  in 
color. 

Obs.  3.  Bring  your  hand  near  the  flame  and  ob- 
serve the  effect. 

Inf.  1.  Infer  what  force  was  developed  by  the 
rubbing  ? 

1.  What  change  immediately  followed  the  rubbing? 
Inf.  2.    Infer  what  force  must  have  caused  the  new 

combinations  of  matter. 

Inf.  3.  Did  the  heat  aid  or  hinder  the  action  of 
this  force  ? 

Inf.  4.  What  force  is  developed  by  the  action  of 
chemical  affinity  ? 

How  do  you  learn  this  fact  ? 

Inf.  5.  What  force  is  made  to  act  by  the  action  of 
this  heat? 

Inf.  6.  How  does  the  amount  of  heat  developed  by 
this  chemical  action  compare  with  the  amount  used  in 
starting  the  action  ? 

2.  State  the  order  in  which  the  different  forces  acted 

in  Experiment  22,  and  the  effect  of  each. 


26  ELEMENTARY   LESSONS  IN   PHYSICS. 

Inf.  7.  In  the  use  of  a  locomotive  to  move  a  train 
of  cars  what  force  acts  first  in  the  fire-box  ? 

Inf.  8.   What  force  is  produced  by  this  action  ? 

Inf.  9.  What  effect  does  the  heat  in  the  water  of 
the  boiler  have  upon  the  train  of  cars  ? 

Call  a  force  applied  through  a  machine  a  mechani- 
cal force. 

Derive  the  term. 

3.  The  heat  produced  in  the  fire  is  here  converted 

into  what  kind  of  force  ? 

4.  Lightning  is  the  action  of  what  force  ? 

5.  When  it  strikes  a  building  what  effect  is  often 

produced  ? 

Inf.  10.  Infer  what  force  must  have  been  developed 
in  order  to  produce  this  effect. 

6.  What  changes  of  force  occur  here  ? 

Inf.  11.  In  producing  electric  light  for  towns  what 
forces  act,  and  in  what  order  ? 

Call  this  relation  of  forces  by  which  one  force  may 
be  converted  into  another  correlation  of  forces. 

Derive  correlation. 

Explain  from  illustrations,  in  writing,  what  is 
meant  by  correlation  of  forces. 

5.     MOLECULAE  ATTRACTION. 

1.   What  two  forms  of  molecular  attraction  have 

we  considered? 
Define  each. 


FORCE.  27 


SOLUTION  AND  CRYSTALLIZATION. 

EXPERIMENT   23.     (At  school.) 

In  two  thirds  of  a  tumbler  of  boiling  water  dis- 
solve as  much  (powdered)  alum  as  you  can. 

Suspend  a  small  string  over  the  middle  of  the 
tumbler,  so  that  it  will  reach  nearly  to  the  bottom  of 
the  liquid. 

Place  the  tumbler  where  it  will  not  be  disturbed, 
and  allow  the  liquid  to  cool  slowly. 

Obs.  Observe  what  forms  upon  the  string,  and 
upon  the  inside  of  the  tumbler. 

Potassium  bichromate,  copper  sulphate,  or  iron  sulphate  may  be 
used  in  place  of  the  alum. 

1.  What  state  of  matter  was  the  alum? 

2.  What  state  of  matter  was  the  water  ? 

3.  What  state  of  matter  did  the  alum  become  in 

the  hot  water? 
Call  such  a  mingling  of  a  solid  with  a  liquid  d 

solution. 

The  term  solution  is  also  applied  to  a  mixture  of  a 
gas  with  a  liquid,  or  to  a  mixture  of  two  liquids. 

Derive  the  term  solution. 

Inf.  1.  What  force  must  have  acted  to  hold  the 
molecules  of  alum  and  water  together  ? 

Inf.  2.  What  force  must  have  been  overcome  in 
forming  this  solution? 

4.  What  force  was  applied  to  aid  the  solution  ? 

5.  When  this  force  disappeared  what  happened  ? 


28  ELEMENTARY  LESSONS   IN   PHYSICS. 

Inf.  3.  What  force  must  have  acted  to  bring  the 
molecules  of  alum  together  again  ? 

Inf.  4.  In  this  experiment  does  heat  act  with  co- 
hesion, or  in  opposition  to  it  ? 

6.    What  kind  of  faces  did  the  solids  formed  from 

this  solution  have  ? 

Call  solids  having  such  faces  and  formed  in  this 
way  crystals. 

Define  crystals. 
Derive  the  term. 

Call  the  process  of  forming  them  crystallization. 

Derive  crystallization. 

CAPILLARY   ATTRACTION. 

EXPERIMENT   34.     (At  home.) 

In  a  pan  or  plate  containing  a  little  water  place  two 
glass  plates  vertically,  so  that,  with  two  of  their  ver- 
tical edges  in  contact,  they  will  form  a  small  angle. 

06s.  1.  Increase  and  diminish  the  size  of  the  an- 
gle, and  observe  the  height  of  the  water  between  the 
plates. 

Inf.  1.    Infer  the  cause. 

06s.  2.    Oil  the  plates,  and  repeat  the  experiment. 

Inf.  2.   Observe  and  infer  as  directed. 

EXPERIMENT  25.     (At  school.) 

Insert  small  glass  tubes  of  different  sizes  in  water, 
in  mercury,  and  in  other  liquids. 

06s.  Observe  the  height  of  each  liquid  in  the 
tubes. 


FORCE.  29 

Inf.    Infer  the  cause  of  the  difference  observed. 

1.  The  attraction  manifest  in  Experiments  24  and 

25  is  between  molecules  of  what  states   of 
matter  ? 

2.  What  is  its  effect  upon  the  liquid  ? 

Call  this  form  of  adhesion  capillary  attraction. 

Describe  it. 
Derive  capillary. 

ABSORPTION  OF   GASES. 

EXPERIMENT  86.     (At  school.) 

Obs.  1.    Observe  the  odor  of  dilute  ammonia  water. 

The  odor  is  due  to  ammonia  gas,  which  is  mixed 
with  the  water  and  is  gradually  escaping  from  it. 

Pour  a  little  of  this  liquid  into  a  test  tube  and  add 
half  as  much  powdered  charcoal. 

FILTER. 

Fold  a  circular  piece  of  filter  paper  (three  or  four 
inches  in  diameter)  upon  its  diameter,  and  fold  it  again 
upon  the  radius  at  right  angles  to  this  diameter. 

Open  it  at  the  circumference  so  as  to  make  a  hollow 
cone,  and  insert  the  apex  in  the  mouth  of  a  horse- 
radish bottle. 

Pour  the  contents  of  the  test  tube  into  the  paper 
cone. 

06s.  2.    Observe  what  happens. 

Call  this  apparatus  a  filter. 

Call  the  liquid  that  passes  through  the  paper  a 
Citrate. 


30  ELEMENTARY   LESSONS   IN   PHYSICS. 

Obs.  3.  Observe  the  odor  of  the  filtrate  and  that  of 
the  charcoal. 

Inf.  1.    Infer  the  cause  of  the  change. 

The  experiment  may  be  repeated  using  hydrogen 
disulphide  in  place  of  ammonia. 

Inf.  2.  What  does  the  charcoal  do  in  these  ex- 
periments ? 

Inf.  3.    What  force  acts  here  ? 

From  this  peculiarity  charcoal  is  used  as  a  de- 
odorizer. 

Derive  this  term. 

Inf.  4.  Infer  why  a  drop  of  oil  on  paper  spreads 
over  the  paper. 

1.   Where  does  the  oil  of  a  lamp  burn  ? 
Inf.  5.   Infer  how  it  gets  there. 

6.     MOLAE  FORCE, 
a.    IMPULSIVE   AND   CONSTANT. 

1.  How  does  the  force  with  which  a  bat  strikes  a 
ball  compare  in  the  length  of  time  which  it 
acts  with  the  force  which  draws  the  ball  to 
the  ground  ? 

Call  a  force  which  acts  only  for  an  instant  an 
impulsive  force. 

Define. 

Derive  the  term. 

Call  a  force  which  acts  continuously  a  constant 
force. 

Define. 
Derive  constant. 


FORCE.  31 

2.  What  kind  of  force  is  the  pressure  of  steam  in  a 

boiler  ? 

3.  The  attraction  of  two  bodies  for  each  other? 

4.  Force  applied  by  a  blow  ? 

b.   TENDENCY  OF   FORCE. 

EXPERIMENT  27.    (At  home.) 

Obs.  Toss  a  ball  gently  upward,  and  observe  care- 
fully any  change  in  the  motion. 

Inf.  1.    What  produced  the  motion  ? 
Inf.  2.    What  caused  the  changes  in  it  ? 

1.  Does   molar   force   always   produce    motion    or 

change  of  motion  ? 

2.  Give  an  instance  in  which  muscular  force  does 

not  produce  either. 

3.  Give   an    instance    in   which    gravity   does   not 

produce  either. 
Inf.  3.    What  is  the  tendency  of  molar  force  ? 

c.   VELOCITY  OF  MOTION. 

1.  How  fast  does  a  train  of  cars  go  ? 

2.  How  fast  does  a  man  walk  ? 

Inf.  1.    Call  the  rate  of  motion  of  a  body  its 

Derive  the  term. 

We  say  that  a  horse  goes  eight  miles  an  hour. 

3.  What  is  an  hour  ? 

4.  What  is  eight  miles  ? 

5.  What  did  we  state  in  giving  the  velocity  of  the 

train  of  cars  ? 


32  ELEMENTARY   LESSONS   IN   PHYSICS. 

UNIFORM,  VARIABLE,  ACCELERATED,  RETARDED. 

6.  How  do  the  distances  which  the  earth  turns  in 

successive  hours  compare  ? 
Call  such  a  rate  of  motion  uniform  velocity. 

7.  What  is  uniform  velocity  ? 

Derive  uniform. 

8.  When  a  train  of  cars  is  getting  under  way,  or 

when  it  is  just  coming  to  a  stop,  how  do  the 
distances  passed  in  successive  seconds  com- 
pare ? 

Call  a  rate  of  motion  at  which  a  body  passes 
over  a  different  distance  in  each  successive 
unit  of  time  variable  velocity. 

9.  Define  variable  velocity. 

Derive  variable. 

10.  Define  accelerated  velocity. 

Derive  the  term. 

11.  Define  retarded  velocity. 

Derive  retarded. 

12.  Give  examples  of  uniform  velocity. 

13.  Give  examples  of  accelerated  velocity. 

14.  Give  examples  of  retarded  velocity. 

Inf.  2.  What  kind  of  velocity  is  produced  by  an 
impulsive  force  acting  alone  ? 

Inf.  3.    By  a  constant  force  acting  alone  ? 

Inf.  4.  By  an  impulsive  and  a  constant  force  acting 
together  in  opposite  directions  ? 

Think  of  a  body  thrown  upward. 


>RCE.  33 


d.    MOMENTUM. 

EXPERIMENT  88.    (At  home.) 

Roll  a  marble  slowly  upon  the  floor  or  oil-cloth. 
Roll  it  twice  as  fast. 

Think  how  much  motion  of  matter  there  is  in  a 
second  in  the  first  case,  and  how  much  in  the  second 
case. 

1.    Compare  the  quantity  of  motion  in  a  second  in 

the  first  case  with  that  in  the  second  case. 
Call  the  quantity  of  motion  of  a  body  in  a  given 
time  its  momentum? 

Derive  momentum. 

Inf.  Infer  one  thing  upon  which  the  momentum 
of  a  body  depends. 

EXPERIMENT  89.    (At  home.) 

Roll  a  small  marble,  and  then  roll  one  two  or  three 
times  as  heavy  at  the  same  rate. 

1.  Compare  the  movements  of  matter  in  a  second 
in  those  two  cases. 

Inf.  Infer  another  thing  upon  which  momentum 
depends. 

e.   INERTIA. 

Inf.  1.  Could  a  moving  body  ever  change  its  ve- 
locity or  direction  of  motion  unless  acted  upon  by 
some  force  ? 

1  The  term  momentum  has  sometimes  been  used  to  mean  the  force 
with  which  a  moving  body  tends  to  overcome  resistance  and  move  on. 
3 


34  ELEMENTARY   LESSONS   IN   PHYSICS. 

Call  the  inability  of  a  moving  body  to  change  its 
motion  inertia  of  motion. 

Define. 

The  term  inertia  is  also  used  in  the  sense  of  the 
tendency  of  a  body  at  rest  to  remain  at  rest,  or  of  a 
body  in  motion  to  continue  the  motion. 

Derive  inertia. 

Inf.  2.  Call  the  inability  of  a  body  at  rest  to  move 
inertia  of 

Define. 

A  man  stood  on  the  bow  of  a  boat  when  it  struck  a 
hidden  rock. 

Inf.  3.   Infer  what  happened,  and  why. 

Inf.  4.  Why  is  it  dangerous  to  step  from  a  moving 
carriage  or  car  ? 

Inf.  5.    How  may  it  be  done  most  safely  ? 

Inf.  6.  An  electric  car  started  suddenly,  and  many 
of  the  standing  passengers  were 

Inf.  7.    Why? 

Inf.  8.  Why  does  a  train  of  cars  start  slowly  and 
acquire  speed  gradually  ? 

Inf.  9.    Why  can  it  not  be  stopped  suddenly  ? 

1.  What  is  the  effect  when   two   rapidly  moving 

trains  meet  upon  the  same  track  ?     Why  ? 

2.  In  driving  a  nail  with  a  hammer  what  is  the 

force  as  it  is  applied  to  the  nail  ? 
Inf.  10.    How   is  the  dust  removed  from  a  carpet 
by  beating  ? 


FORCE.  35 

/.   RESISTANCE. 
OF  THE  AIR. 

EXPERIMENT   3O.    (At  home.) 

Move  a  fan  edgewise  quickly  through  the  air. 
Obs.    Move  it  at  the  same  rate  in  the  usual  way, 
and  observe  any  difference  in  the  force  required. 
Inf.  1.    Infer  what  causes  this  difference. 
Call  that  which  hinders  motion  resistance. 

Define. 

Derive  resistance. 

Call  the  resistance  in  this  experiment  resistance  of 
the  air. 

Inf.  2.    It  is  really  due  to  what  property  of  the  air  ? 

OF  INERTIA. 

Inf.  3.  To  what  is  the  greater  part  of  the  resist- 
ance in  starting  a  train  of  cars  due  ? 

Call  it  resistance  of  inertia. 

Inf.  4.  What  does  the  amount  of  this  resistance 
depend  upon  ? 

OF  FRICTION. 

EXPERIMENT  3t.    (At  home.) 

Tie  one  end  of  a  string  around  a  book. 

Obs.  Holding  the  other  end  in  the  fingers,  draw 
the  book  by  the  string  slowly  and  with  uniform 
motion  over  the  carpet,  and  notice  whether  any  force 
is  reqiiired  after  inertia  has  been  overcome. 

Inf.    Infer  why  this  force  is  required. 

Call  this  resistance  the  resistance  of  friction. 

Derive  this  term. 


36  ELEMENTARY   LESSONS   IN    PHYSICS. 

OF  MUSCULAR  FORCE. 

EXPERIMENT  32.    (At  home.) 

Obs.  Repeat  Experiment  31,  pressing  with  the  fin- 
gers of  the  other  hand  slightly  against  the  forward 
end  of  the  book,  and  observe  any  difference  in  the 
force  required  to  move  the  book. 

Inf.   Infer  what  this  difference  is  due  to. 

OF   GRAVITY. 

EXPERIMENT  33.    (At  home.) 

Raise  the  book  vertically  by  the  string. 

Inf.  1.    What  is  the  resistance  chiefly  due  to  ? 

Inf.  2.  If  the  book  weighs  two  pounds  and  you 
lift  with  a  force  of  three  pounds,  what  becomes  of 
the  surplus  force  which  gravity  does  not  resist  ? 

Inf.  3.  How  much  of  this  surplus  will  be  used  up 
in  that  way  ? 

luf.  4.  How,  then,  does  the  sum  of  all  the  dif- 
ferent forms  of  resistance  compare  with  the  force 
resisted  ? 

Inf.  5.  How  does  the  direction  of  the  resistance 
compare  with  that  of  the  moving  force  ? 

Newton  has  expressed  these  facts  by  saying  that 
action  and  reaction  are  equal  and  in  opposite  direc- 
tions. 

Inf.  6.    What  can  he  mean  by  action  and  reaction? 


FORCE.  37 

g.  MEASURE  OF  FORCE. 

EXPERIMENT  34.      (At  school.) 

Make  a  spring  of  No.  22  brass  wire  by  winding  it 
closely  upon  a  pencil. 

Cut  the  string  used  in  Experiment  31  between  the 
book  and  the  end  held  in  the  fingers,  and  fasten  the 
ends  thus  made  to  the  ends  of  the  spring. 


Fig.  9. 


Obs.  1.  Repeat  Experiment  31,  and  ascertain  by  a 
rule  how  much  the  spring  is  stretched. 

Obs.  2.  Draw  the  book  over  the  smooth  surface  of 
a  table,  and  see  how  much  the  spring  is  stretched. 

Inf.  1.  Compare  carefully  the  forces  used  in  the 
two  parts  of  this  experiment. 

1.    What  is  the  unit  used  in  the  measure  of  gravity  ? 

Other  molar  forces  are  measured  by  the  same  unit. 

EXPERIMENT  35.     (At  home.) 

Make  a  one-pound,  a  two-pound,  and  a  five-pound 
weight,  by  weighing  out  the  right  quantities  of  pebbles 
in  tin  cans. 

Lift  these  weights  successively,  and  note  the  force 
required  in  each  case. 

1.  Compare  a  force  that  will  sustain  one  pound 
with  one  which  will  support  two  pounds; 
with  one  which  will  support  five  pounds. 


ELEMENTARY  LESSONS  IN  PHYSICS. 


h.   WORK. 

Inf.  1.  What  forms  of  resistance  must  be  overcome 
in  drawing  a  double-runner  up  hill  ? 

Call  the  overcoming  of  resistance  of  any  kind 
work. 

Inf.  2.  a.  How  does  the  work  of  raising  a  pound 
one  foot /compare  with  the  work  of  raising  it  four 
feet? 

b.  With  that  of  raising  it  ten  feet  ? 

c.  With  that  of  raising  two  pounds  two  feet  ? 

d.  With  that  of  raising  three  pounds  ten  feet  ? 

1.  What  two  things  must  be  considered  in  meas- 

uring work  ? 

2.  What  is  the  unit  of  work  with  which  we  have 

compared  the  work  in  each  of  these  cases  ? 
Call  this  unit  a,  foot-pound. 

Define. 

3.  How  many  foot-pounds  of  work  in  each  of  the 

above  cases  ? 

f.  POWER. 

Inf.  1.  Which  can  do  more  work  in  an  hour,  a 
horse  or  a  locomotive? 

The  rate  at  which  an  agent  can  do  work  is  spoken 
of  as  its  power. 

Define. 

Inf.  2.  In  measuring  power  what  must  we  con- 
sider besides  units  of  work  done? 


FORCE.  S9 

One  foot-pound  of  work  in  a  second  is  a  unit  of 
power. 

In  measuring  the  power  of  agents  capable  of  doing 
a  large  amount  of  work  550  foot-pounds  of  work  in 
a  second  is  taken  as  the  standard.  This  is  called  a 
horse-power. 

Define. 

An  engine  of  one  horse-power  is  capable  of  acting 
through  one  foot  in  a  second  against  a  resistance  of 
550  pounds,  or  of  acting  through  550  feet  in  a  second 
against  a  resistance  of  one  pound. 

1.  How  far  can  it  raise  275  pounds  in  a  second  ? 

2.  How  far  can  it  raise  1100  pounds  in  a  second  ? 

3.  How   far  .can   it   raise    1100    pounds    in    ten 

seconds  ? 

4.  How   many  pounds  can  a  twenty  horse-power 

engine  raise  ten  feet  in  a  second  ? 

j.   ENERGY. 

Inf.  Think  how  it  is  that  a  moving  body,  a  bent  or 
coiled  spring,  or  a  lifted  weight  can  do  work. 
Call  the  ability  to  do  work  energy. 

Define. 

Derive  the  term. 


*.   COMPOSITION  OF   FORCES. 

From  a  strip  of  sheet  lead,  cut  three  pieces  an  inch 
square,  two  pieces  1x2  inches,  two  pieces  1x3 


40 


ELEMENTARY   LESSONS   IN   PHYSICS. 


inches,  two  pieces  1x4  inches,  and  two  pieces  1x6 
inches ;  and  make  a  hole  with  an  awl  through  one 
corner  of  each  piece. 

Make  a  wooden  frame  two  feet  long  and  sixteen 
inches  high,  and  attach  two  small  pulleys  to  the  top 
of  the  frame  a  foot  apart,  as  shown  in  Figure  10. 


Fig.  10. 


Equilibrium. 

EXPERIMENT  36.      (At  school.) 

Pass  a  short  string  over  one  of  the  pulleys  and  tie  » 
hook  made  of  a  bent  pin  to  each  end  of  it. 

Hang  a 'strong  envelope  upon  one  hook,  and  upon 
the  other  hang  an  inch  lead  and  a  two-inch  lead. 

Pour  into  the  envelope  as  much  sand  as  the  two 
leads  will  balance. 

When  all  the  forces  acting  upon  a  body  balance 
each  other,  it  is  said  to  be  in  equilibrium. 

Derive  the  term. 


FORCE.  41 

Resultant. 

1.  Do  the  two  leads  act  in  the  same  or  in  different 

lines  ? 

2.  In  the  same  or  in  opposite  directions  ? 

Obs.  Find  a  single*  force  which  will  produce  the 
same  effect  as  these  two. 

Call  it  a  resultant  of  the  two. 

Define. 

Derive  resultant. 

Components. 

Call  the  original  forces  the  components  of  the 
resultant. 

Define.     (A  force  may  have  more  than  two  components.) 
Derive  the  term  components. 

Two  Forces  in  Same  Line. 

IN  SAME  DIRECTION. 

Inf.  1.  Resultant  of  two  forces  acting  in  same  line 
in  same  direction  equals  what  ?  (See  Obs.,  above.) 

Acts  where  ?  and  in  what  direction  ? 

Suppose  a  boat  is  rowed  down  stream  at  the  rate  of 
four  miles  an  hour,  and  the  current  carries  it  two 
miles  an  hour. 

Inf.  2.    With  what  velocity  does  it  proceed  ? 

IN  OPPOSITE  DIRECTION. 

EXPERIMENT  37.      (At  school.) 

Pass  the  string  over  the  pulley,  and  hang  a  two- 
inch  lead  on  one  end  and  a  six-inch  lead  on  the  other. 


42  ELEMENTARY  LESSONS  IN  PHYSICS. 

Hang  an  envelope  on  the  hook  with  the  lighter 
weight,  and  pour  into  it  sand  enough  to  produce 
equilibrium. 

Obs.  Remove  the  two  lead  weights,  and  find  their 
resultant,  and  apply  it. 

1.  This  is  the  resultant  of  what  ? 

2.  It  equals  what  ?  acts  where  ?  in  what  line  ? 

A  boat  sails  through  the  water  at  the  rate  of  eight 
miles  an  hour  against  a  current  of  three  miles  an 
hour. 

Inf.  1.    What  is  its  actual  rate  of  progress  ? 

A  steamer  propelled  by  a  force  that  would  carry  her 
ten  miles  an  hour  is  held  back  by  a  wind  that,  acting 
alone,  would  carry  her  astern  at  the  rate  of  four  miles 
an  hour. 

Inf.  2.  How  long  will  it  take  her  to  go  twenty- 
eight  miles  ? 

Two  Parallel  Forces. 

IN  SAME  DIRECTION. 

EXPERIMENT  38.       (At  school.) 

On  the  same  side  of  a  light  wooden  bar  thirteen 
inches  long  place  two  small  screw-eyes  twelve  inches 
apart. 

On  the  opposide  side  of  the  bar  insert  three  more 
screw-eyes  at  intervals  of  three  inches  from  the  first 
and  from  each  other. 

Pass  cords  from  the  end  screw-eyes  over  the  pulleys, 
in  the  frame  used  in  Experiment  36,  and  balance 


FORCE.  43 


1 

1 

6 

Fig    11. 

6 

the  bar  in  a  horizontal  position  by  small  weights  on 
the  cords. 

Obs.  On  one  of  these  cords  hang  a  two-inch  lead, 
and  on  the  other  a  six-inch  lead;  and  find  what 
weight  they  will  balance,  and  where  it  must  be 
placed  to  keep  the  bar  horizontal. 

Inf.  1.  From  this  infer  what  the  resultant  must 
be. 

A  force  of  100  pounds  and  a  force  of  200  pounds 
act  in  parallel  lines  in  the  same  direction. 

Inf.  2.  Their  resultant  is  a  force  of  ....  pounds 

acting  in  the  .....  direction,  in  a  line as 

far  from  the  line  of  the  greater  force  as  from  that  of 
the  smaller. 

Two  Forces  at  an  Angle. 

A  boat  is  rowed  across  a  river  at  the  rate  of  six 
feet  a  second,  and  carried  down  stream  by  the  current 
at  the  rate  of  three  feet  a  second. 

1.  Draw  a  line  on  paper,  starting  from  a  given 
point  a,  to  represent  the  direction  in  which 
the  boat  would  have  moved  and  the  distance 
which  the  rowing  would  have  carried  it  in 
three  seconds  without  any  current,  and  mark 
the  end  b. 


44  ELEMENTARY  LESSONS   IN  PHYSICS. 

Draw  another  line,  starting  from  the  same  point, 

to  show  in  what  direction  and  how  far  the 

current  would  have   carried    it   without   the 

rowing,  and  mark  the  end  c. 
Consider  the  rowing  and  the  current  as  acting 

at  the  same  time. 
How  far  across  the  river  and  how   far   down 

the  river  will  it  have  been  carried  in  twenty 

seconds  ? 

Mark  its  actual  position  at  the  end  of  that  time  d. 
Draw  a  line  showing  the  actual  path  in  which 

the  boat  has  moved. 
Connect  d  with  b  and  c  by  straight  lines. 

2.  What  figure  have  you  drawn  ? 

3.  What  does  the  diagonal  represent  ? 

4.  What  do  the  sides  ab  and  ac  represent  ? 

Inf.  Infer  how  the  resultant  compares  with  the  sum 
of  the  components,  and  with  the  difference  of  the 
components. 

5.  How  does  its  direction  compare  with  the  direc- 

tions of  the  components  ? 


GRAVITY. 


45 


VI.    GRAVITY. 

1.    Recall  definition  and  derivation  of  gravity. 
2.   CENTEE   OF  GRAVITY. 

EXPERIMENT  39.    (At  home.) 

Suspend  a  weight  from  a  fixed  point  by  a  thread 
about  twelve  inches  long,  with  a  small  loop  in  the 
thread  just  below  the  point  of  support. 


Fig.  12. 

Stick  a  pin  through  a  piece  of  card-board  near  one 
edge,  and  hang  it  in  the  loop  so  that  the  thread  will 
be  in  front  of  the  card- board. 


46  ELEMENTARY  LESSONS  IN  PHYSICS. 

Mark  upon  the  card-board  the  position  of  the  thread 
below  the  loop. 

Stick  the  pin  through  some  other  part  of  the  card- 
board near  the  edge,  hang  it  in  the  loop,  and  mark 
as  before. 

Place  the  intersection  of  these  marks  on  the  point  of 
a  pin,  and  see  if  it  will  balance  in  different  positions. 

If  not,  repeat  the  experiment,  taking  care  to  mark 
the  positions  of  the  thread  exactly. 

Call  the  point  at  which  a  body  may  be  supported  in 
any  position  its  centre  of  gravity. 

Define. 

3.   LINE  OF   DIRECTION. 

Call  the  line  passing  through  the  centre  of  gravity 
of  a  body  and  the  centre  of  the  earth  the  line  of  di- 
rection of  the  body. 

Define. 

4.   EQUILIBRIUM, 
a.     OF   A   BODY   SUPPORTED   AT   ONE   POINT. 

EXPERIMENT  4O.    (At  home.) 

Stick  a  pin  through  the  card  used  in  Experiment 
39,  at  its  centre  of  gravity,  and  pin  it  against  a  verti- 
cal surface  so  that  it  will  turn  easily  on  the  pin. 

Obs.  1.    In  what  positions  is  it  in  equilibrium  ? 

Obs.  2.  In  the  same  way  support  the  card  an  inch 
from  the  centre  of  gravity,  and  find  in  what  positions 
it  is  in  equilibrium. 


GRAVITY.  47 

STABLE  EQUILIBRIUM. 

Obs.  3.  In  what  direction  from  the  centre  of  gravity 
is  the  support  when  the  greatest  force  is  required  to 
overturn  the  body  ? 

Inf.  1.  Why  is  more  force  required  to  disturb  the 
equilibrium  with  the  body  in  this  position  ? 

A  body  so  supported  is  said  to  be  in  stable  equi- 
librium. 

Derive  stable. 

UNSTABLE   EQUILIBRIUM. 

Obs.  4.  In  what  direction  from  the  centre  of  gravity 
is  the  support  applied  when  least  force  is  required  to 
overturn  the  body  ? 

Inf.  2.  Why  is  less  force  required  with  the  support 
applied  there  ? 

A  body  so  supported  is  said  to  be  in  unstable 
equilibrium. 

Derive  unstable. 

NEUTRAL  EQUILIBRIUM. 

Obs.  5.  Where  is  the  support  applied  when  the 
body  is  balanced  in  any  position  ? 

A  body  so  supported  is  said  to  be  in  neutral  equi- 
librium. 

Derive  neutral. 

b.     OF   A  BODY  RESTING  ON  ITS  BASE. 

1.    In    what    position    is    a   book   in    most    stable 

equilibium  ? 

Inf.  1.  In  what  position  of  the  book  will  the  centre 
of  gravity  have  to  be  raised  most  to  overturn  it  ? 


48  ELEMENTARY  LESSONS  IN  PHYSICS. 

Inf.  2.  In  what  position  of  the  book  would  the 
centre  of  gravity  have  to  be  raised  least  to  over- 
turn it  ? 

Inf.  3.  Is  a  tall  body  more  or  less  stable  than  a 
short  body  ?  Why  ?  (See  Inf.  1  and  2.) 

Inf.  4.  Is  a  body  with  a  large  base  more  or  less 
stable  than  one  with  a  small  base  ?  Why  ? 

Inf.  5.  Through  what  point  of  the  base  must  the 
line  of  direction  pass  that  the  body  may  be  as  stable 
as  possible  ? 

Inf.  6.  Will  a  body  stand  if  the  line  of  direction 
passes  outside  the  base  ? 

Inf.  7.  The  stability  of  a  body  resting  on  its  base 
depends  upon  what  ? 

Inf.  8.  Why  are  legs  of  chairs  and  stools  made  to 
slant  outward  ? 

A  young  lady  placed  a  step  ladder  in  the  position 
shown  in  Figure  13,  and  it  stood. 


Fig.  13. 


GRAVITY.  49 

Inf.  9.  Infer  where  the  line  of  direction  passed 
with  regard  to  the  base. 

The  young  lady  proceeded  to  mount  the  steps. 
Inf.  10.    Infer  what  happened,  and  why. 

5.   FALLING  BODIES. 

Inf.  11.    What  causes  bodies  to  fall? 
1,    What  kind  of  a  force  is  gravity  ? 
Inf.  12.  Infer  with  what  kind  of  velocity  a  body 
will  fall? 

EXPERIMENT  41.     (At  home.) 

Obs.  Get  some  one  to  drop  a  body  from  an  ele- 
vated position,  and,  standing  at  a  little  distance, 
observe  the  rate  of  fall  carefully. 

1.   Does  your  observation  agree  with  your  inference? 

6.   PENDULUM. 
a.    DEFINITIONS. 

EXPERIMENT  42.     (At  home.) 

By  means  of  a  thread  suspend  a  light  weight  from  a 
fixed  point,  so  that  the  centre  of  gravity  of  the  weight 
will  be  eighteen  inches  from  the  point  of  support. 

Obs.  Pull  the  weight  aside  ;  let  go,  observe  the 
effect,  and  describe  it  carefully. 

Call  a  body  suspended  from  a  fixed  point  so  as  to 
swing  freely  a  pendulum. 

Define. 

Derive  pendulum. 


50  ELEMENTARY   LESSONS  IN   PHYSICS. 

Call  one  swing  of  a  pendulum  a  vibration. 

Define. 

Derive  vibration. 

b.  CAUSE  OF  VIBRATION. 

Inf.   Infer  what  causes  a  pendulum  to  vibrate. 

c.  RATE   OF   VIBRATION. 
EFFECT  OF  LENGTH  OP  ARC. 

EXPERIMENT  43.     (At  home.) 

Obs.  1.  Pull  the  pendulum  three  inches  aside,  let 
go,  and  count  the  vibrations  for  thirty  seconds. 

Obs.  2.  Pull  the  pendulum  six  inches  aside,  let  go, 
and  count  the  vibrations  for  thirty  seconds. 

Inf.  Infer  whether  the  rate  of  vibration  is  affected 
by  the  length  of  arc  through  which  the  pendulum 
swings. 

EFFECT  OF  WEIGHT  OF  PENDULUM. 

EXPERIMENT  44.     (At  home.) 

Obs.  Suspend  a  heavier  weight  so  as  to  make  a 
pendulum  of  the  same  length,  and  see  how  many 
vibrations  it  will  make  in  thirty  seconds. 

Inf.  Infer  whether  the  weight  of  the  pendulum 
affects  the  rate  of  vibration. 

EFFECT  OF  LENGTH  OF  PENDULUM. 

EXPERIMENT  45.     (At  home.) 

Obs.  1.  Lengthen  the  pendulum  and  see  how  the 
rate  of  vibration  is  affected. 


GRAVITY.  51 

Obs.  2.  Make  the  pendulum  four  times  as  long  as 
at  first,  and  see  how  the  rate  of  vibration  is  affected. 

EXPERIMENT  46.     (At  home.) 

Obs.  1.  By  trial  find  a  pendulum  of  such  length 
that  it  will  make  one  vibration  a  second. 

How  long  is  it  ? 

Obs.  2.  Find  a  pendulum  that  will  vibrate  half- 
seconds. 

How  long  is  it  ? 

USE  OF  THE  PENDULUM. 

1.  How  does  the  number  of  vibrations  made  by  a 
pendulum  in  one  minute  compare  with  the  number 

,  made  in  any  other  minute  ? 

2.  How    then,    would   you   say   the  pendulum  vi- 
brates ? 

3.  By  reason  of  this  fact  it  is  adapted  to  what 
use  ? 

Describe  its  use  as  a  metronome. 

Derive  metronome. 

USE  ix  CLOCKS. 

EXPERIMENT  47.      (At  school.) 

Wind  a  clock,  and  start  it.  Notice  how  it  goes  for 
a  minute  or  two. 

Obs.  Remove  the  hands  and  face  of  the  clock,  and 
observe  how  the  pendulum  is  connected  with  the 
works. 


52  ELEMENTARY   LESSONS   IN    PHYSICS. 

Inf.  1.    What  is  the  tendency  of  the  coiled  spring? 

Inf.  2.  What  is  the  relation  of  the  spring  to  the 
works  ? 

Inf.  3.  Infer  what  would  happen  if  there  were  no 
pendulum  ? 

Inf.  4.    Infer  the  use  of  the  pendulum. 

7.  PEESSURE   OF   LIQUIDS. 
a.    FACT   OF   PRESSURE. 

EXPERIMENT  48.     (At  school.) 

Over  the  large  end  of  a  small  lamp  chimney  tie  a 
piece  of  sheet  rubber  such  as  may  be  obtained  of  a 
dentist. 


Fig.  14. 


Fit  a  cork  stopper  water-tight  into  the  small  end 
of  the  chimney. 

Perforate  the  cork  near  one  side  with  a  rat-tail  file, 
and  fit  tightly  a  short  glass  tube. 

Over  the  end  of  this  tube  draw  one  end  of  a  piece 
of  rubber  tubing  about  two  feet  long. 


GRAVITY.  53 

Draw  the  other  end  of  this  tubing  over  the  tube  of 
a  small  tunnel  supported  by  means  of  a  crayon  box 
or  stand,  as  in  Figure  14. 

Loosen  the  stopper  a  little  so  that  air  may  escape, 
and  pour  into  the  tunnel  water  enongh  to  fill  the 
chimney,  the  tube,  and  the  tunnel ;  and  press  the  stop- 
per in  tight. 

Obs.  1.    Observe  the  effect  upon  the  sheet  rubber. 

Inf.  1.   Infer  the  cause  of  this. 

b.    DIRECTIONS  OF  PRESSURE. 

Obs.  2.  Keeping  the  sheet  rubber  at  the  same  dis- 
tance below  the  level  of  the  surface  of  the  water  in 
the  tunnel,  turn  the  chimney  so  that  it  will  be  hori- 
zontal, and  observe  the  effect  upon  the  sheet  rubber. 

Do  not  claim  to  observe  what  you  infer. 

Inf.  2.    What  causes  this  ? 

Obs.  3.  Keeping  the  rubber  at  the  same  level,  turn 
the  chimney  so  that  the  rubber  will  be  upward,  and 
observe. 

Inf.  3.    Infer  the  cause. 

Inf.  4.   In  what  directions  does  water  at  rest  press? 

c.    UPON  WHAT  PRESSURE   DEPENDS. 

EXPERIMENT  49.     (At  school.) 

Obs.  Slowly  lower  the  chimney  farther  below  the 
level  of  the  surface  of  the  water,  and  observe  the 
effect  upon  the  sheet  rubber. 


54  ELEMENTARY  LESSONS  IN  PHYSICS. 

Inf.  What  does  pressure  of  a  liquid  at  rest  depend 
upon  ?  i.  e.  how  does  it  vary  ? 

EXPERIMENT  50.     (At  school.) 

In  the  gas  or  alcohol  lamp  flame,  heat  a  piece  of 
small  glass  tubing  about  two  inches  from  the  end,  and 
when  it  becomes  soft  draw  it  out  to  a  point. 

When  it  is  cooled,  break  off  the  small  end  of  the 
two-inch  piece,  so  as  to  leave  an  opening  about  one 
sixteenth  of  an  inch  in  diameter. 

Fit  the  large  end  of  this  tube  into  the  cork  stopper 
in  the  end  of  the  chimney. 

Obs.  I.  Fill  the  chimney,  tube,  and  tunnel  with 
water,  and  observe  what  the  water  does. 

Obs.  2.  Lower  and  raise  the  chimney,  and  observe 
the  effect. 

Inf.   Infer  the  cause  of  this  action. 

d.    SURFACE  OF  LIQUID  IN  COMMUNICATING  VESSELS. 

EXPERIMENT  51.     (At  school.) 

Remove  the  short  glass  tube  from  the  cork,  and 
insert  one  about  two  feet  long. 

Obs.  1.  Holding  the  chimney  and  this  long  tube 
upright,  fill  the  chimney,  rubber  tube,  and  tunnel 
with  water,  and  observe  the  height  of  the  water  in 
the  glass  tube. 

Obs.  2.  Slowly  raise  and  lower  the  tunnel,  and 
compare  the  height  of  the  water  in  the  glass  tube 
with  its  height  in  the  tunnel. 


GRAVITY.  55 

e.  WATER  WORKS   FOR  CITIES   AND  TOWNS. 

Describe  with  diagrams  the  water  works  of  your 
city  or  town,  representing  the  pumping  station,  stand- 
pipe  or  reservoir,  mains,  hydrants,  and  pipes  in  a  house. 

Inf.  1.    Where  is  the  presure  in  the  pipes  greatest  ? 

Inf.  2.    How  high  will  water  rise  in  the  pipes  ? 

Inf.  3.  Where  would  water  be  thrown  highest  from 
a  hose  connected  with  a  hydrant  ? 

/.  THE  SPIRIT  LEVEL. 

Examine  a  spirit  level. 

Obs.  1.    Of  what  parts  does  it  consist  ? 

The  liquid  in  the  tube  is  alcohol,  and  the  bubble 
is  air. 

Inf.    Why  is  alcohol  better  than  water  ? 

Obs.  2.  When  the  bubble  is  in  the  middle  of  the 
tube,  what  is  the  position  of  the  case  ? 

1.    How  is  the  level  used  ? 

g.  SPRINGS   AND  WELLS. 

What  becomes  of  the  water  that  falls  upon  the 
land  as  rain  ? 

The  portion  of  it  which  sinks  into  the  ground 
works  down  through  soil,  loam,  sand,  or  gravel,  and 
comes  to  a  layer  of  material,  a  a,  in  the  diagram, 
through  which  it  does  not  readily  pass. 

It  works  its  way  along  the  slope  of  this  impervious 
layer,  through  the  loose  material  which  rests  upon  it, 
and  may  reach  the  surface  at  some  lower  level,  as  at  a'. 


66 


ELEMENTARY   LESSONS   IN   PHYSICS. 


Call  the  water  flowing  out  at  the  surface  a  spring. 
Suppose  the  water  tills  the  loose  material  to  the 
level  c  cf. 


Fig.  15. 


Inf.  1.  If  a  hole  is  dug  down  through  this  ma- 
terial, as  at  w,  what  will  till  the  lower  part  of  the 
hole? 

Inf.  2.  To  what  level  ? 

Call  such  a  hole  extending  down  below  the  level 
of  the  water  in  the  earth  a  . 


ARTESIAN  WELLS. 


Sometimes  a  layer  of  loose  material,  as  s/,  in- 
cluded between  two  layers  of  earth  impervious  to 
water,  is  exposed  at  the  surface  along  one  edge,  as 


Fig.  16. 

at  /,  and  stretches  down  an  extended  slope,  perhaps 
for  many  miles. 


GRAVITY.  57 

The  exposed  portion  of  this  layer  may  cover  a  large 
area. 

What  will  become  of  the  water  which  falls  upon 
this  exposed  portion  of  the  stratum  ? 

Suppose  a  hole  be  bored  through  the  close  layer 
above  at  some  lower  point,  as  at  a. 

Inf.  1.    Infer  what  the  effect  would  be. 

Call  such  a  well  an  Artesian  ivell. 

Derive  this  name. 

Inf.  2.  What  force  acts  to  produce  springs  and 
wells  ? 

h.   FLOATING  AND  SINKING. 

EXPERIMENT  52.     (At  school.) 

Upon  a  convenient  support  four  or  five  feet  from 
the  floor  hang  the  spring  balance,  so  that  it  will  not 
be  within  four  or  five  inches  of  a  wall. 

Upon  the  hook  of  the  balance  hang  a  quart  tin  pail, 
and  observe  its  weight. 

Below  the  pail  suspend  a  pebble  a  little  smaller 
than  the  pail  and  observe  its  weight. 

Set  another  pail,  large  enough  to  contain  the  peb- 
ble, in  a  basin,  and  fill  this  pail  just  full  of  water. 
Holding  the  balance  in  the  hand,  lower  it  until  the 
pebble  is  covered  with  the  water. 

Obs.  1.  Observe  what  happens  to  the  water  and  to 
the  spring. 

Inf.  1.  Infer  how  large  a  volume  of  water  is  dis- 
placed. 


58 


ELEMENTARY   LESSONS   IN   PHYSICS. 


Inf.  2.  Has  the  pebble  gained  or  lost  in  weight 
by  being  immersed  in  the  water  ?  How  much  ? 

Obs.  2.  Remove  the  pail  from  the  basin,  and,  again 
holding  the  balance  so  that  the  pebble  is  immersed, 
pour  the  water  from  the  basin  into  the  empty  pail, 
and  notice  the  effect  upon  the  balance. 


Fig.  17. 


in 


Inf.  3.  How  does  the  weight  of  the  pebble  m 
water,  together  with  the  weight  of  the  water  dis- 
placed, compare  with  the  weight  of  the  pebble  in  air? 


GRAVITY.  59 

Repeat  this  experiment  using  a  mass  of  iron  in 
place  of  the  pebble. 

Inf.  4.  How  does  the  loss  of  weight  of  a  solid 
immersed  compare  with  the  weight  of  an  equal 
volume  of  the  liquid  ? 

Inf.  5.  A  solid  having  the  same  weight  as  its  own 
volume  of  the  liquid  will  lose  how  much  of  its  weight 
on  being  immersed  ? 

Inf.  6.    Will  it  float,  or  sink  ? 

Inf.  7.    If  it  will  float,  at  what  level  ? 

Inf.  8.  Will  a  body  heavier  than  water  float  in 
water,  or  sink  ? 

Inf.  9.  Will  a  body  lighter  than  water  float,  or 
sink? 

Inf.  10.   Will  it  project  above  the  liquid  ? 

Inf.  11.  A  body  half  as  heavy  as  water  will  float 
with  what  part  of  it  above  water  ? 

Inf.  12.  Since  a  piece  of  sheet  tin  or  of  iron 
sinks  in  water,  how  can  a  tin  pan  or  an  iron  ship 
float? 


«.    SPECIFIC   GRAVITY. 
OF  SOLIDS. 

Divide  the  weight  of  the  pebble  in  air,  in  the  pre- 
ceding experiment,  by  the  weight  of  an  equal  volume 
of  water. 

Call  the  quotient  the  specific  gravity  of  the  pebble. 

Derive  the  term. 


60  ELEMENTARY   LESSONS  IN   PHYSICS. 

Find  the  specific  gravity  of  a  mass  of  iron  weighing 
two  or  three  pounds. 

a.  Think  how  you  can  find  the  weight  of  an  equal 

volume  of  water. 

b.  Think  how  you  can  proceed  to  find  the  specific 

gravity  of  the  iron. 

c.  Find  it. 

1.  State  how  to  find  the  specific  gravity  of  solids 
heavier  than  water. 

Inf.  13.  Suppose  a  body  floats  with  half  of  its  vol- 
ume under  water,  what  is  its  specific  gravity  ? 

Inf.  14.  If  it  floats  with  an  eighth  of  its  volume 
under  water,  what  is  its  specific  gravity  ? 

Inf.  15.  If  a  body  floats  with  five  sixths  of  its  vol- 
ume out  of  water,  what  is  its  specific  gravity  ? 

A  convenient  spring  balance  for  finding  the  specific  gravity  of  small 
specimens  of  minerals  and  metals'  may  be  made  as  follows. 

Cut  out  a  piece  of  board  (pine  or  white  wood)  about  6  inches  square, 
and  another  piece  about  16  inches  long,  and  1|  inches  wide  at  one  end 
and  1  inch  at  the  other  end. 

Nail  the  wide  end  of  this  strip  to  the  middle  of  one  edge  of  the 
square,  so  that  it  will  stand  upright  with  the  square  as  a  base,  as  shown 
in  the  figure. 

Near  the  top  of  this  standard  insert  horizontally  a  screw-eye  of  small 
wire  1^  inches  long,  with  eye  opened  so  as  to  form  a  hook. 

Make  a  spring  by  winding  brass  wire,  No.  25  to  28,  close  about  a 
pencil,  and  keeping  it  wound  for  a  minute  or  two. 

Hang  the  spring  by  one  end  of  the  coil  upon  the  hook. 

Bend  the  end  of  the  wire  at  the  lower  end  of  the  coil  into  a  hori- 
zontal position,  so  that  it  will  project  as  an  index  in  front  of  the 
standard. 

Mark  off  a  scale  upon  this  standard  from  the  level  of  the  index 
downward,  by  drawing  horizontal  lines  ^  of  an  inch  apart  and  num- 
bering every  fifth  line. 


GRAVITY. 


61 


By  means  of  a  noose  of  horse  hair  or  fine  thread,  suspend  the 
specimen  from  the  lower  end  of  the  spring,  and  see  how  many  degrees 
it  stretches  the  spring,  i.  e.  how  many  units  of  weight  it  has. 

Raise  a  tumbler  partly  filled  with  water  under  the  specimen  until 
it  is  immersed,  and  thus  get  its  loss  of  weight  in  water. 


Fig.  18. 
OF  LIQUIDS. 

EXPERIMENT   53.     (At  school.) 

1.  Weigh  a  small-mouthed  bottle. 

2.  Fill  it  with  water  and  weigh  it. 

3.  Fill  it  with  saturated  brine  and  weigh  it. 

4.  Find  the  specific  gravity  of  the  brine. 

5.  Find  the  specific  gravity  of  alcohol,  of  linseed 

oil,  and  of  kerosene. 


62  ELEMENTARY  LESSONS   IN   PHYSICS. 


8.    PKESSUKE   OF   AIR 
a.   FACT  OF   PRESSURE. 

EXPERIMENT   54.     (At  school.) 

Over  the  mouth  of  a  T.  D.  clay  pipe,  tie,  air-tight, 
a  piece  of  sheet  rubber. 

Obs.  1.  Taking  the  stem  of  the  pipe  in  the  mouth, 
with  the  bowl  upright, "  draw  out "  through  the  stem 
as  much  air  as  you  can,  and  observe  the  effect  upon 
the  sheet  rubber. 

Inf.  1.    Infer  what  causes  this  effect. 

b.    DIRECTIONS   OF  PRESSURE. 

Obs.  2.    Turn  the  bowl  of  the  pipe  downward,  draw 
out  the  air,  and  observe  the  effect. 
Inf.  2.    Infer  the  cause  of  this. 
Repeat  this  with  the  bowl  in  various  positions. 
Inf.  3.    In  what  directions  does  the  air  press  ? 

c.   EFFECTS   OF   PRESSURE. 

EXPERIMENT  55.     (At  home.) 

Fill  a  tumbler  with  water,  cut  a  piece  of  card-board 
a  little  larger  than  the  top  of  the  tumbler,  and  lay  it 
over  the  top. 

With  the  palm  of  the  hand  hold  it  against  the  edge 
of  the  tumbler  without  pressing  the  middle  of  it  in, 
invert  the  tumbler,  and  remove  the  hand. 


GRAVITY.  6F 

Obs.    Observe  the  effect. 

Inf.   Infer  why  the  water  does  not  fall  out. 

EXPERIMENT  56.    (At  school.) 

Insert  a  small  glass  tube  in  water,  and  note  the 
height  of  the  water  in  the  tube. 

Place  the  thumb  over  the  top,  and  raise  it  vertically 
out  of  the  water. 

Obs.    Observe  whether  the  water  remains  in  the  tube. 

Inf.    Infer  the  cause. 

EXPERIMENT  57.  (At  home.) 

Fill  a  tumbler  with  water,  invert  it  under  water, 
and,  holding  it  even,  raise  it  until  the  mouth  is  nearly 
even  with  the  top  of  the  water. 

Obs.    Observe  the  height  of  the  water  in  the  tumbler. 

Inf.  1.    What  sustains  the  water  there  ? 

Inf.  2.    What  force  causes  the  pressure  of  the  air  ? 

BAROMETER. 

EXPERIMENT  58.    (At  school.) 

By  means  of  a  short  piece  of  rubber  tubing,  connect 
the  tube  of  a  small  glass  tunnel  with  one  end  of  a 
heavy  glass  tube  33  or  34  inches  long,  and  closed  at 
the  other  end. 

Fill  the  tube  with  mercury. 

If  there  are  air  bubbles  in  the  tube,  remove  them 
by  inserting  a  slender  iron  wire. 

Holding  the  finger  firmly  over  the  end  of  the  tube, 


tJ4  ELEMENTARY  LESSONS   IN   PHYSICS. 

so  that  no  mercury  can  run  out,  invert  the  tube,  and 
insert  the  open  end  of  it  in  a  cup  of  mercury. 

Obs.  1.    Notice  the  height  of  the  mercury  in  the 
tube. 

Inf.  1.  Why  does  it  not  all  run  out  of  the 
tube? 

Inf.  2.    Why  does  it  not  entirely  fill  the  tube? 
Obs.  2.    Measure  the  height  of  the  mercury 
in  the  tube  above  the  surface  of  the  mercury 
in  the  cup. 

It  is  found  by  experiment  that  the  height  of 
the  column  of  mercury  is  not  affected  by  the  size 
of  the  tube,  but  varies  slightly  for  all  tubes  at 
different  times. 

/;/.  3.  What  does  the  height  of  the  mercury 
column  depend  upon  ?  (See  Inf.  1  and  2.) 

Inf.  4.  What  does  the  variation  in  the  height 
of  the  mercury  indicate  ? 

Thus  the  height  of  the  mercury  column  be- 
Fj  comes  a  measure  of  the  atmospheric  pressure. 

For  this  use  the  tube  is  attached  to  a  case 
with  a  graduated  scale  at  the  top  to  indicate  the 
height  of  the  mercury  column  in  inches;  and  the 
whole  apparatus  is  called  a  barometer. 

Describe  it,  and  derive  the  name. 

EXPERIMENT  59.      (At  school.) 

Place  the  barometer  where  it  will  not  be  disturbed, 
and  note  the  changes  in  the  height  of  the  mercury 
and  the  changes,  in  the  weather  for  a  few  weeks. 


GRAVITY.  65 

Ols.  What  correspondence  in  these  changes  can 
you  discover  ? 

Inf.  What  inferences  in  regard  to  the  weather  can 
you  make  from  changes  in  the  barometer  ? 

PUMPS. 
LIFTING  PUMPS. 

EXPERIMENT  6O     (At  school.) 

Into  an  even  glass  tube  fit  a  piston  with  a  rod  a 
little  longer  than  the  tube. 

Holding  the  tube  in  the  left  hand,  push  the  piston 
through  the  tube  so  that  it  will  be  even  with  the  end 
of  the  tube. 

Obs.  Holding  this  end  steadily  under  water,  slowly 
raise  the  piston,  and  observe  the  effect  in  the  tube. 

Inf.    What  causes  this  ? 

If  you  have  a  glass  lifting  pump,  or  can  buy  one, 
use  it.  If  not,  a  good  one  may  be  made  by  careful 
work. 

To  MAKE  A  LIFTING  PUMP. 

Fit  two  small  screw-eyes  with  rather  long  screws  into  the  end  of 
a  spool  1  inch  or  1^  inches  in  diameter,  as  shown  in  Figure  20. 

Cut  out  a  piece  of  sheet  rubber  ^  x  f  of  an  inch ;  lay  one  end  of 
this  upon  the  flat  surface  of  a  block  of  pine  |  X  I  X  y8^  of  an  inch, 
and  fasten  it  to  the  block  by  a  single  small  tack  in  the  centre.  (See 
Fig-are  20.) 

Lay  this  block,  rubber-side  down,  over  the  hole  in  the  end  of  the 
spool  between  the  screw-eyes ;  and  with  two  small  tacks  fasten  the 
projecting  portion  of  the  rubber  to  the  end  of  the  spool,  so  as  to  form 
a  little  valve  opening  from  the  spool  and  covering  the  hole  in  the  spool 
when  closed. 

5 


66 


ELEMENTARY  LESSONS   IN   PHYSICS. 


Get  a  piece  of  pine  10  inches  long  and  \  inch  square  at  one  end, 
and  at  the  other  end  £  inch  thick  and  wide  enough  to  fill  the  space 
between  the  screw-eyes. 

Place  the  wide  end  of  the  rod  between  the  screw-eyes,  and  fasten  it 
by  small  screws  passing  through  the  screw-eyes,  taking  care  to  have 
the  end  of  the  rod  far  enough  from  the  spool  to  allow  the  valve  to 
open  at  least  \  of  an  inch. 

Round  off  the  rod  with  a  knife,  and  wind  upon  the  spool  enough 
twine  to  a  little  more  than  fill  it. 


Fig.  20. 


Fig.  21. 


Fig.  22. 


Call  this  apparatus  the  piston  of  your  pump. 

Select  a  lamp  chimney  such  as  is  shown  in  Figure  21,  of  the  same 
diameter  throughout  the  straight  part. 

To  test  the  evenness  of  chimneys  fit  the  piston  into  them  and  work 
it  carefully  up  and  down,  noticing  whether  the  fit  is  equally  close 
throughout. 

Fit  tightly  a  cork  into  the  large  end  of  the  chimney. 


GRAVITY.  67 

Perforate  this  cork  with  a  rat-tail  file,  and  fit  a  glass  tube  8  or  10 
inches  long  into  it  water-tight,  as  shown  in  Figure  22. 

Make  a  valve  covering  the  top  of  this  tube  like  the  valve  in  the  top 
of  the  piston. 

Insert  the  cork  into  which  the  tube  has  been  fitted  in  the  large  end 
of  the  chimney. 

With  a  triangular  file  make  a  hole  through  the  side  of  the  chimney 
about  2  inches  from  the  top,  then  with  a  rat-tail  file  round  out  the 
hole  so  as  to  make  it  elliptical,  and  insert  in  it  a  short  piece  of  rubber 
tube  for  a  spout. 

EXPERIMENT   61.    (At  school  ) 

Having  made  sure  that  the  piston  and  the  cork  are 
tight,  take  the  chimney  in  the  left  hand  and  the 
piston  rod  in  the  right,  and  inserting  the  glass  tube 
below  the  surface  of  the  water,  carefully  work  the 
piston  up  and  down. 

Obs.  1.  Observe  the  position  of  each  valve  as  the 
piston  is  raised,  and  as  it  is  lowered. 

If  no  change  is  observed,  work  the  piston  faster, 
and  notice  carefully. 

Inf.  1.    Infer  the  cause  of  the  changes. 

Obs.  2.    Observe  the  change  in  the  water. 

Inf.  2.    Infer  the  cause  of  this  change. 

NOTE.  — To  say  that  the  water  is  "drawn  up,"  or  "sucked  up,"  is 
not  giving  any  cause. 

If  a  pipe  33  feet  or  more  in  length,  closed  at  one 
end  and  open  at  the  other,  be  filled  with  water,  and, 
with  the  open  end  kept  under  water,  the  closed  end 
be  raised  until  it  is  brought  to  a  vertical  position,  it 
has  been  found  that  the  water  will  continue  to  fill  the 
pipe  to  the  height  of  about  32  feet  above  the  level  of 
the  water  outside  of  the  pipe. 


68 


ELEMENTARY  LESSONS  IN   PHYSICS. 


Inf.  3.  Infer  what  keeps  the  water  up  to  that 
height. 

Inf.  4.  Why  does  it  not  sustain  a  higher  column 
of  water  ? 

Inf.  5.  About  how  high  should  you  think  water 
could  be  raised  with  a  lifting  pump  ? 

Is  it  ever  necessary  to  raise  water  higher  than 
that? 

FORCE  PUMP. 
To  MAKE  A  FORCE  PUMP. 

Fit  a  rod  about  10  inches  long  into  a  spool  1  inch  in  diameter,  as  in 
Figure  23.  Wind  the  spool  full  of  twine,  and  select  a  lamp  chimney 
of  even  bore,  as  for  the  lifting  pump. 


Fig.  23. 

Fit  the  bottom  of  the  chimney  tightly  with  a  firm  cork,  and  fit  the 
cork  with  a  tube  and  valve,  as  in  the  lifting  pump. 

Fit  tightly  a  firm  cork  into  a  horse-radish  bottle. 

Connect  the  lower  part  of  the  chimney  with  the  bottle  by  a  glass 
tube,  bent  as  shown  in  Figure  24,  and  fitted  tightly  into  the  stop- 
pers. 

Over  the  end  of  this  tube  in  the  bottle  place  a  valve  like  that  in  the 
chimney. 

Make  another  hole  in  the  cork  in  the  bottle  and  fit  into  it  tightly 
a  glass  tube  5  or  6  inches  long,  bent  as  shown  in  the  figure,  and  drawn 
out  to  a  small  size'  at  the  end  b,  Figure  24 

EXPERIMENT  62.      (At  school.) 

Having  made  sure  that  the  piston,  corks,  and  tubes 
are  all  tight,  hold  the  chimney  in  the  left  hand,  insert 


GRAVITY. 


69 


the  tube  a  under  water,  and  work  the  piston  carefully 
with  the  right  hand. 

Obs.  1.  Observe  the  action  of  each  valve  and  the 
movement  of  the  water  as  the  piston  is  raised  and  as 
it  is  pressed  downward. 


Fig.  24. 


Inf.  1.    Infer  the  cause  of  each  change  observed. 

Obs.  2.    What  is  in  the  upper  part  of  the  bottle  ? 
Call  the  bottle  an  air-chamber. 
Inf.  2.    Of  what  advantage  is  it  ? 


70  ELEMENTARY  LESSONS  IN  PHYSICS. 

Inf.  3.  What  kind  of  pump  is  used  at  a  pumping 
station  ? 

1.  What  do  fire-engines  for  throwing  water  con- 
sist of? 

Write  a  connected  description  of  each  kind  of 
pump,  illustrating  by  drawings. 


SIMPLE   MACHINES.  71 

VII.     SIMPLE   MACHINES. 

1.    LEVERS. 

a.     DEFINITIONS. 

+ . 

LEVER. 

EXPERIMENT  63.      (At  home.) 

Place  a  pencil  or  rule  upon  a  book  so  that  one  end 
of  it  will  project  about  3  inches  beyond  the  edge  of 
the  book. 


By  raising  and  lowering  the  ends   of  the  pencil, 
turn  it  about  the  edge  of  the  book  as  a  fixed  support. 
Call  a  bar  so  arranged  a  lever. 

Define. 

Derive  the  term. 

FULCRUM. 

Call  the  support  upon  which  it  turns  the  fulcrum 
of  the  lever. 

Define. 
Derive  fulcrum. 

LOAD  AND  POWER. 

EXPERIMENT  64.      (At  home.) 

Place  another  book  upon  the  projecting  end  of  the 
lever,  and  press  down  with  the  fingers  upon  the  other 
end. 


72 


ELEMENTARY  LESSONS   IN   PHYSICS. 

Obs.    Observe  the  effect. 

Call  the  second  book  the  load  of  the  lever. 

Call  the  force  applied  to  support  the  load  the  power. 

1.  In  the  above  experiment  what  was  the  position 

of  the  fulcrum  with  reference  to  the  load  and 
the  power  ? 

2.  Use  your  pencil  as  a  lever  with  the  load  between 

the  power  and  the  fulcrum. 

3.  Use  it  as  a  lever  with  the  power  between  the 

load  and  the  fulcrum. 


b.  RELATION  OF  POWER  TO  LOAD. 

EXPERIMENT  65.      (At  school.) 

Insert  a  small  screw-eye  in  the  middle  of  a  light 
wooden  bar  13  inches  long. 

Suspend  the  bar  by  this  screw-eye  from  the  middle 
of  the  frame  used  in  Experiment  36. 


Fig.  26. 

If  the  bar  does  not  balance  in  a  horizontal  position, 
whittle  down  the  heavier  arm  until  it  does. 


SIMPLE   MACHINES.  73 

On  the  under  side  of  this  bar  cut  little  notches  2, 
4,  and  6  inches  from  the  screw-eye  towards  each  end. 

Bend  one  end  of  a  six-inch  lead  weight  into  a  hook, 
and  hang  it  as  a  load  upon  the  bar,  so  that  the  mid- 
dle of  the  end  of  the  lead  will  be  at  a  notch  2  inches 
from  the  fulcrum. 

Obs.  1.  Find  what  power  applied  at  the  same  dis- 
tance from  the  fulcrum  will  balance  this  load. 

Obs.  2.  Find  what  power  applied  twice  as  far  from 
the  fulcrum  will  balance  the  load. 

1.  Compare  it  with  the  load. 

Obs.  3.  Find  what  power  applied  three  times  as 
far  from  the  fulcrum  will  balance  the  load. 

2.  Compare  it  with  the  load. 

Inf.  How  does  the  power  required  to  balance  the 
load  vary  as  the  distance  of  the  power  from  the 
fulcrum  increases  ? 

Obs.  4.  Find  what  power  in  each  of  the  above 
positions  will  raise  the  load. 

Obs.  5.  How  do  the  distances  moved  by  the  power 
and  load  in  each  of  the  above  positions  compare  ? 

When  the  power  required  to  balance  a  load  is  half 
as  great  as  the  load,  the  distance  which  it  passes  in 

moving  the  load  is as  great  as  that  passed 

by  the  load. 

EXPERIMENT  66.      (At  school.) 

Obs.  1.  Find  what  load  placed  2  inches  from  the 
fulcrum  a  power  of  2  units  applied  2  inches  from  the 
fulcrum  will  balance. 


74  ELEMENTARY  LESSONS  IN  PHYSICS. 

Obs.  2.  Applied  4  inches  from  the  fulcrum,  it  will 
balance  what  load  2  inches  from  the  fulcrum  ? 

Ols.  3.  Applied  6  inches  from  the  fulcrum,  it  will 
balance  what  load  2  inches  from  the  fulcrum  ? 

EXPERIMENT  67.     (At  school.) 

06s.  Place  the  load  twice  as  far  from  the  fulcrum 
as  in  the  last  experiment,  and  see  how  the  power 
required  at  any  point  to  balance  it  is  affected. 

c.    APPLICATIONS. 

CROW-BAR. 
Describe  the  crow-bar  and  its  use. 

STEELYARD. 

Show  where  the  fulcrum  is  in  the  steelyard. 

Where  the  load  is  applied. 

Where  the  power  is  applied. 

How  the  weight  of  the  load  is  shown. 

2.    WHEEL  AND  AXLE, 
a.    CONSTRUCTION. 

The  wheel  and  axle  consists  of  two  connected 
cylinders  of  different  diameters  turning  upon  a  com- 
mon axis,  as  shown  in  Figure  27. 

The  larger  cylinder  is  called  the  wheel,  and  the 
smaller  one  the  axle. 


SIMPLE   MACHINES. 


75 


Fig.  27. 

The  wheel  and  axle  may  be  made  as  follows  :  — 

Get  a  turner  to  turn  for  you  in  one  piece  two  cylinders,  each  1  inch 
long,  and  one  1  inch  and  the  other  3  inches  in  diameter,  as  shown  in 
Figure  28. 

At  the  inner  end  of  the  smaller  cylinder  drive  a  large  gimp  tack, 
allowing  the  head  to  project  a  little. 


- — 2- — y 


Fig.  28. 


In  the  middle  of  the  opposite  side  of  the  larger  cylinder  drive  a 
small  gimp  tack. 

Make  a  small  hole  with  an  awl  in  the  axis  of  the  cylinders  at  each 
end. 

Cut  out  a  piece  of  board  4  inches  long,  and  3  inches  wide  at  one  end 
and  1  inch  at  the  other.  This  piece  is  marked  a  in  Figure  27. 

Place  this  piece  in  position,  as  shown  in  the  figure,  2^  inches  from 
the  end  of  the  frame,  and  fasten  it  with  screws  through  the  top  of  the 
frame. 


76  ELEMENTARY  LESSONS  IN  PHYSICS. 

With  an  awl  make  a  horizontal  hole  half  an  inch  above  the  middle 
point  of  the  lower  end  of  this  piece,  and  another  hole  in  the  same  line 
with  this,  in  the  end  of  the  frame. 

Place  the  wheel  and  axle  in  position,  and  fasten  it  by  inserting  wire 
nails  through  the  holes  in  the  frame  into  the  ends  of  the  cylinders. 

If  it  does  not  turn  easily  pull  out  the  wire  nails  and  make  the  holes 
in  the  frame  a  little  larger. 

b.   RELATION  OF   POWER   TO   LOAD. 

Tie  a  string  12  inches  long  to  the  tack  in  the 
wheel,  and  another  to  the  tack  in  the  axle. 

In  experimenting,  let  these  strings  draw  around 
the  wheel  and  axle  in  opposite  directions. 


EXPERIMENT  68.      (At  school.) 

Obs.  1.  Hang  a  load  of  6  units  upon  the  string 
the  axle,  and  find  what  power  applied  to  the 
string  on  the  wheel  will  balance  it. 

Obs.  2.   Find  what  power  will  raise  it. 

Obs.  3.  In  moving  the  load  1  inch  the  power 
moves  how  far? 

1.  The  load  is  applied  how  far  from  the  axis  ? 

2.  The  power  is  applied  how  far  from  the  axis  ? 
Inf.  I.   The  axis  of  the  wheel  and  axle  corresponds 

to  what  in  the  lever? 

Inf.  2.  The  radius  of  the  axle  in  this  experiment 
corresponds  to  what  in  the  lever  ? 

Inf.  3.  The  radius  of  the  wheel  corresponds  to 
what  in  the  lever? 

In  the  above  experiment  the  power  was  applied 
,  ,  ,  ,  times  as  far  from  the  axis  as  the  load,  and  a 


on 


SIMPLE   MACHINES.  77 

power  ...  as  great  as  the  load  was  required  to 
balance  it. 

Inf.  4.  How  does  the  relation  of  power  to  load  in 
the  wheel  and  axle  compare  with  the  relation  of 
power  to  load  in  the  lever  ? 

Inf.  5.  How  far  can  a  load  be  moved  with  one  ap- 
plication of  the  lever  ? 

Inf.  6.  How  far  with  one  application  of  the  wheel 
and  axle  ? 

Inf.  7.  What  advantage  has  the  wheel  and  axle 
over  the  lever  ? 

Inf.  8.    For  what  uses  is  the  lever  better  adapted  ? 

EXPERIMENT  69.     (At  school.) 

Place  a  load  of  3  units  upon  the  wheel. 

Obs.  1.  Find  what  power  applied  on  the  axle  will 
balance  it. 

Obs.  2.    Find  what  power  will  move  it. 

Obs.  3.  In  raising  the  load  6  inches  how  far  does 
the  power  move  ? 

1.  How  do  these  results  compare  with  those  ob- 
tained with  the  lever? 


c.   APPLICATIONS. 

What  uses  of  any  form  of  wheel  and  axle  have  you 
seen? 

Write  a  composition  upon  the  Uses  of  the  Wlieel  and 
Axle,  illustrating  the  various  forms  by  drawings, 


78  ELEMENTARY  LESSONS  IN  PHYSICS. 

3.    PULLEYS. 
a.    DESCRIBE. 

Examine  one  of  the  pulleys  in  the  frame  which  we 
have  used,  and  tell  what  it  consists  of. 

FIXED   PULLEY. 

Call  a  pulley  which  remains  in  the  same  place 
when  in  use  a  fixed  pulley. 

MOVABLE  PULLEY. 

Call  a  pulley  which  changes  its  place  when  in  use  a 
movable  pulley. 

A  good  set  of  pulleys  is  desirable.  If  these  are  not  to  be  had,  brass 
pulleys  carefully  selected  from  such  as  may  be  found  at  any  hardware 
store,  and  at  many  country  stores,  will  do. 

To  adapt  these  for  use  as  movable  pulleys  wind  one  end  of  a  piece 
of  Jg-inch  wire  8  inches  long  about  the  shaft  just  below  the  pulley. 
Bend  the  wire  over  the  pulley,  as  shown  in  Figure  29,  wind  it  down 
around  the  shaft,  and  bend  the  end  into  a  hook. 


r.  29 


SIMPLE   MACHINES. 


79 


b.    RELATION   OF  POWER   TO   LOAD. 
IN  FIXED  PULLEYS. 

EXPERIMENT   7O.     (At  school.) 

Draw  a  pliable  string  over  a  fixed  pulley. 

Fasten  a  load  of  6  units  to  one  end  of  the  string. 

Obs.  1.  Find  what  power  applied  at  the  other  end 
will  balance  it. 

Obs.  2.    Find  what  power  will  raise  it. 

Inf.  Why  is  a  greater  power  required  to  raise  a 
load  than  to  balance  it  ? 


EXPERIMENT   71.      (At  school.) 

Pass  the  cord  over  three  fixed  pulleys,  as  shown 
in  Figure  30. 


Fig.  30. 

Hang  a  load  upon  one  end  of  the  cord. 
Obs.  Find  what  power  applied  at  the  other  end  will 
balance  it. 


80 


ELEMENTARY  LESSONS  IN  PHYSICS. 


Inf.  Infer  what  power  will  balance  any  load  when 
acting  through  a  cord  passing  over  any  number  of 
fixed  pulleys. 

IN  COMBINATIONS  OF  FIXED  AND  MOVABLE  PULLEYS. 

EXPERIMENT   73.     (At  school.) 

Fasten  one  end  of  the  string  to  the  top  of  the 
frame. 

Draw  the  other  end  under  a  movable  pulley  and 
over  a  fixed  pulley,  as  indicated  in  Figure  31. 

Fasten  to  the  string  a  weight  which  will  balance 
the  weight  of  the  movable  pulley. 


Fig.  31. 


Hang  a  load  of  2  pounds  on  the  movable  pulley. 
Obs.  1.   Find  what  power  will  balance  it. 
1.    Compare  the  power  and  load. 
Obs.  2.    The  movable  pulley  is  supported  by  how 
many  parts  of  the  cord? 


SIMPLE  MACHINES. 


81 


EXPERIMENT  73.     (At  school.) 

Support  the  movable  pulley  by  three  parts  of  the 
cord,  as  shown  in  Figure  32. 

Obs.  1.  Balance  the  weight  of  the  movable  pulley, 
and  find  how  the  power  which  will  balance  a  load, 
compares  with  the  load. 


Fig.  32.1 

Obs.  2.   In  raising  the  load  how  do  the   distances 
passed  by  the  power  and  load  compare  ? 


c.  USE  OF  PULLEYS. 

Inf.  1.    Of  what  use  are  fixed  pulleys? 

Inf.  2.  What  advantage  is  there  in  the  use  of  a 
combination  of  fixed  and  movable  pulleys  ? 

Write  an  illustrated  account  of  the  ways  in  which 
you  have  seen  pulleys  applied. 

1  The  fixed  pulleys  should  be  near  enough  together  to  make  the 
parts  of  the  cord  draw  vertically. 
6 


82  ELEMENTARY  LESSONS  IN  PHYSICS. 

4.    INCLINED   PLANE. 

Get  a  piece  of  board  6  X  24  inches. 

Fasten  a  pulley  in  the  middle  of  one  end  of  it,  as 
shown  in  Figure  33. 

Place  the  board  upon  a  table  with  the  pulley  pro- 
jecting 3  inches  beyond  the  end  of  the  table. 


Fig.  33. 

Eaise  the  end  containing  the  pulley  4  inches  higher 
than  the  other  end  of  the  board,  and  support  it  with 
books  placed  under  it. 

Call  the  top  of  this  board  an  inclined  plane. 

a.  RELATION  OF  POWER  TO  LOAD. 

EXPERIMENT  74.     (At  school.) 

Upon  this  plane  place  a  toy  car  or  carriage  with  a 
string  fastened  to  it  and  passing  over  the  pulley. 

Obs.  1.    Let  go  the  string,  and  observe  the  effect. 

Balance  the  car  by  a  weight  upon  the  string. 

Place  upon  the  car  a  can  or  box  of  pebbles  weigh- 
ing 3  pounds. 


SIMPLE   MACHINES.  83 

Obs.  2.  Find  what  power  applied  at  the  end  of  the 
string  will  balance  this  load. 

1.  How  does  it  compare  with  the  load  ? 

2.  How  does  the  height  of  the  plane  compare  with 

the  length  of  the  plane  ? 

Inf.  Infer  why  the  power  required  is  less  than  the 
load. 

EXPERIMENT  75.     (At  school.) 

Raise  the  end  of  the  inclined  plane  4  inches  higher; 
and  repeat  the  experiment,  comparing  the  power  with 
the  load  and  the  height  of  the  plane  with  its  length. 

b.   USE. 
1.   Where  have  you  seen  inclined  planes  used  for 

raising  loads? 
Inf.  Of  what  advantage  are  they  ? 

5.    SCREW. 

It  is  well  for  the  school  to  own  a  small  jack-screw 
or  bench-screw.  If  that  is  not  practicable,  one  may 
be  borrowed  of  some  mechanic  or  building  mover. 

1.  Turn  the  screw  partly  out  of  the  nut,  and  ex- 

amine it.     What  is  its  general  shape  ? 

2.  What  is  there  upon  the  outside  of  this  cylinder  ? 
Call  this  spiral  projection  the  thread  of  the  screw. 

3.  Notice    the    upper   and   lower   surfaces   of    the 

thread  as  they  wind  around  the  cylinder. 
Are  they  level,  or  inclined  ? 
What  do  they  form  ? 


84  ELEMENTARY  LESSONS  IN   PHYSICS. 

4.  Remove  the  screw  and  examine  the  inside  of 
the  nut. 

What  do  you  find  for  the  thread  of  the  screw  to 
fit  into? 

Figure  34  represents  a  jack-screw  as  it  would  ap- 
pear if  the  front  half  of  the  upper  part  of  the  nut 
could  be  removed,  showing  a  vertical  section  of  the 
nut  and  the  front  of  the  screw. 


Pig.  34. 

5.  What  does  the  screw  rest  upon  ? 

6.  What  does  the  under  side  of  the  thread  slide 

over  when  the  screw  is  turned  ? 
See  if  you  can  raise  a  load  with  a  jack-screw. 
Explain  fully  by  diagram  how  it  is  done. 


SIMPLE  MACHINES.  85 

6.    WEDGE. 

Examine  a  wedge. 

1.  Compare  it  with  the  inclined  plane. 

2.  For  what  have  you  seen  it  used  ? 

3.  In  its  use  is  the  load  moved  over  the  wedge  ? 

4.  What  is  moved  ? 

5.  How  is  it  moved  ? 

APPLICATIONS  OF   THE  SIMPLE  MACHINES. 

1.  Which  of  these  machines  have  you  seen  used 

in    raising    loads    to    the    upper    stories    of 
buildings  ? 

2.  A  door  key  belongs  to.  which  of  these  classes 

of  machines? 

3.  Which  machines  have  you  seen   used  for  rais- 

ing and  lowering  the  wicks  of  lamps? 

4.  Which  would  you  use  for  splitting  wood  ? 

5.  Which  is  used  in  moving  a  building  along  the 

street  ? 

6.  What  other  simple  machine  is  used  in  working 

a  jack-screw  ? 

7.  What  machine  would  you  use  in  loading  a  barrel 

of  oil  upon  a  truck  ? 

8.  What  machines  have  been  used  for  raising  "  the 

old  oaken  bucket "  from  the  well  ? 

9.  In   which    of   the   simple   machines   is  the    re- 

sistance of  friction  least? 
10.    Can  any  machine  furnish  energy? 


86  ELEMENTARY  LESSONS  IN  PHYSICS. 

Write  an  explanation  of  the  advantages  in  the  use 
of  simple  machines,  giving  examples  and  illustrating 
by  diagrams.  Show  that : 

1.  They  enable  us  to  do  slowly  heavier  work  than 

we  could  do  without  them,  or  to  do  light 
work  more  rapidly  than  we  could  without 
them. 

2.  They  enable  us  to  use  a  force  at  a  more  con- 

venient point  and  in  a  more  convenient  di- 
rection than  we  could  otherwise  use  it. 

3.  They  enable  us  to  employ  other  forces  than  our 

own  in  doing  work. 


HEAT.  87 


HEAT. 
1.   SOUECES   OF   HEAT. 

EXPERIMENT  76.    (At  home.) 

Obs.  Hold  the  back  of  your  hand  in  the  sunshine 
for  a  minute,  and  then  in  the  shade,  and  notice  the 
difference. 

Inf.   What  is  one  source  of  heat  ? 

EXPERIMENT  77.    (At  home.) 

Repeat  Experiment  21. 

Inf.   What  is  another  source  of  heat  ? 

EXPERIMENT   78.    (At  home.) 

Touch  a  nail  to  your  cheek. 

Hammer  one  end  of  it  upon  an  anvil  for  a  few 
seconds,  and  touch  it  to  the  cheek  again. 

Obs.    Observe  the  change. 

Inf.  1.    Infer  a  third  source  of  heat. 

In  our  study  of  Correlation  of  Forces  we  noticed  two 
other  sources  of  heat. 

1.  What  are  they  ?    » 

2.  Name  the  sources  of  heat  which  we  have  con- 

sidered. 

Inf.  2.  From  which  of  these  sources  do  we  get 
most  heat? 

Inf.  3.  From  which  do  we  get  the  next  greatest 
supply  ? 


88  ELEMENTARY  LESSONS  IN   PHYSICS. 

2.  EFFECTS   OF  HEAT. 

a.    EXPANSION. 

(1)   OF  SOLIDS. 

EXPERIMENT   79.     (At  home.) 

Bend  one  end  of  a  wire  10  inches  long  into  a  ring 
just  large  enough  so  that  a  marble  will  not  drop 
through  it. 


Fig.  35. 

Obs.  1.    Heat  the  ring  hot,  and  see  if  the  marble 
will  drop  through. 

Inf.  1.    Infer  the  cause. 

Inf.  2.   What  is  one  effect  of  heat  ? 

Derive  the  terra  expansion. 

Obs.  2.   Cool  the  ring,  and  see  if  the  marble  will 
drop  through. 

Inf.  3.  Infer  the  cause  of  this. 

1.  Give  other  instances  in  which  you  have  noticed 

that  heat  expands  solids. 

2.  In  laying  the  rails  of  a  railroad  what  allowance 

is  made  on  account  of  this  fact  ? 

3.  Do  you  know  of  any  uses  made  of  this  fact  in 

the  arts? 

(2)    OP  LIQUIDS. 

EXPERIMENT  80. 

Fill  a  large  test  tube  with  cold  water. 

Insert  a  stopper  into  which  has  been  fitted  a  small 


HEAT.  89 

glass   tube,  so  that  the  water  will  rise  in  the  tube 
above  the  stopper. 

Heat  the  test  tube  gently. 

06s.  1.    Observe  the  effect  on  the  water. 


Fig.  36. 

Inf.  1.   What  causes  this  ? 

06s.  2.    Cool  the  test  tube,  and  observe. 

Inf.  2.   Infer  the  cause  of  this  change. 

EXPERIMENT  81.     (At  home.) 

Warm  a  thermometer  bulb. 

Obs.  1.    Observe  the  mercury  in  the  tube. 

Inf.  1.   Infer  the  cause  of  the  change. 

06s.  Inf.  2.    Cool  the  bulb,  observe,  and  infer. 

1.  Describe  the   thermometer,   telling   what  parts 

it   consists   of,    describing   each,   and  telling 
how  it  works. 

2.  Give  other  instances  in  which  you  have  noticed 

that  heat  expands  liquids. 


90  ELEMENTARY  LESSONS  IN  PHYSICS. 

(3)  OF  GASES. 

EXPERIMENT  82.    (At  school.) 

Fill  the  apparatus  used  in  Experiment  80  with  air. 
insert  the  glass  tube  beneath  the  surface  of  water, 
and  warm  the  test  tube. 

Obs.   What  is  the  effect  ? 

Inf.    What  causes  this  action  ? 

1.  What  effect  of  heat  is  shown  in  Experiments 
79,  80,  81,  and  82? 

6.    CHANGES  IN  STATES  OF  MATTER. 

Liquefaction. 

EXPERIMENT  83.     (At  home.) 

Heat  a  little  ice  in  a  tin  can  or  cup. 
Obs.   State   the   effect,  and   give    a   name   to   the 
change. 

Derive  the  name. 

Inf.  What  would  be  the  effect  if  this  heat  were 
given  out  from  the  water? 

The  change  of  a  liquid  to  a  solid  is  called  solidi- 
fication. 

Derive  solidification, 

EXPERIMENT  84.     (At  school.) 

Heat  a  little  lead  in  an  iron  spoon. 

06s.  1.  Observe  the  change. 

Obs.  2.  Allow  the  lead  to  cool,  and  observe  the 
change. 


HEAT.  91 

1.    Give  other  instances  in  which  heat  changes  the 
state  of  matter. 

EFFECT  OF  MELTING  ON  ADJACENT  BODIES. 

EXPERIMENT  85.      (At  home.) 

In  a  tin  can  mix  ice,  broken  into  small  pieces,  with 
about  half  its  weight  of  salt. 

Obs.  1.    Watch  the  change  for  a  few  minutes. 

Obs.  2.  Then  insert  your  finger  in  the  mixture, 
and  note  the  temperature. 

Into  a  small  test  tube  pour  a  few  drops  of  water. 

Insert  it  in  the  mixture,  and  leave  it  for  a  few 
minutes. 

Obs.  3.  Observe  the  effect  on  the  water  in  the  test 
tube. 

Inf.  1.    Infer  the  cause  of  this  change. 

Inf.  2.  Infer  the  effect  of  melting  upon  adjacent 
bodies. 

1.    What  use  is  made  of  this  fact  ? 

Inf.  3.  What  effect  does  the  melting  of  ice  and 
snow  have  upon  the  temperature  of  the  air  ? 

Vaporization. 
BOILING. 

EXPERIMENT  86.     (At  school.) 

Half  fill  a  test  tube  with  water,  and  heat  it  care- 
fully by  holding  it  obliquely  in  the  flame  for  5 
minutes. 


92  ELEMENTARY  LESSONS  IN  PHYSICS. 

Obs.  1.  Observe  what  rises  from  the  tube,  and  the 
quantity  of  water  left  in  the  tube. 

Inf.   Infer  what  change  in  the  state  of  matter  was 
produced. 
•  Call  this  change  vaporization. 

Derive  the  term. 

Obs.  2.  Describe  carefully  the  process  as  it  occurs 
in  this  experiment. 

What  is  formed  within  the  liquid  ?    Rapidly  ?    Or  slowly  ? 

Call  this  process 

NOTE.  —  Some  pupils  may  try  additional  experiments  to  determine 
the  boiling  points  of  different  liquids,  and  what  the  boiling  point  of 
any  liquid  depends  upon. 

EVAPORATION. 

EXPERIMENT  87.     (At  home.) 

Place  a  little  water  in  a  shallow  tin  plate,  and  heat 
it  gently,  without  boiling,  for  half  an  hour. 

Obs.  Observe  what  forms,  and  the  quantity  of 
water  remaining. 

Inf.   Infer  what  change  is  taking  place. 

1.   How  does  the  process  differ  from  boiling? 

Call  it  evaporation. 

Derive  the  name. 

NOTE. —  Some  pupils  may  investigate  the  influences  which  affect 
evaporation. 

EFFECT  OF  VAPORIZATION  ON  ADJACENT  BODIES. 

EXPERIMENT  88.      (At  school.) 

Place  a  drop  of  water  on  a  piece  of  shaving. 
On  the  drop  rest  a  thin  watch  crystal  with  a  few 
drops  of  ether  in  it. 


HEAT.  93 

With  the  mouth  about  8  inches  from  the  ether, 
blow  steadily  across  its  surface  until  it  has  all 
evaporated. 

Obs.  Observe  the  effect  upon  the  water  under  the 
crystal. 

Inf.  1.    Infer  the  cause  of  this  change. 

1.  How    does   sprinkling   the   floor   or   the    street 

affect  the  temperature  of  the  air? 

2.  How  does  a  summer  shower  affect  the  temper- 

ature ? 

Inf.  2.    Why? 
Explain  the  manufacture  of  artificial  ice. 

CONDENSATION, 

EXPERIMENT   89.      (At  home.) 

Obs.    Vaporize   some   water,   hold   a  piece  of  cold 
glass  in  the  escaping  vapor,  and  observe  the  effect. 
Inf.    Infer  the  cause  of  this. 
1.    What  new  change  in  the  state  of  matter  occurs 

in  this  experiment? 
Name  the  change  condensation. 

Derive  the  name. 

DEW,  DEW  POINT,  FROST,  CLOUDS,  RAIN,  HAIL,  SNOW. 

EXPERIMENT  9O.      (At  school.) 

Half  fill  a  tin  fruit  can  with  water  at  a  temper- 
ature of  about  60  degrees. 

Place  a  chemical  themometer  in  the  water,  and  add 
small  bits  of  ice  gradually  until  moisture  begins  to 
collect  on  the  outside  of  the  can. 


94  ELEMENTARY   LESSONS   IN   PHYSICS. 

Call  this  moisture  dew. 

Call  the  temperature  at  which  it  begins  to  form 
i\\Q'  dew  point. 

Inf.  1.   Infer  the  cause  of  the  deposit. 

Inf.  2.    Account  for  the  dew  on  the  grass. 

Inf.  3.    Account  for  frost. 

Inf.  4.  If  cold  air  meets  warm  air,  what  is  the 
effect  upon  the  warm  air? 

Inf.  5.    Upon  the  moisture  in  the  air  ? 

Inf.  6.   Infer  how  rain  is  formed  ;  hail ;  snow. 

3.   TRANSFER  OF  HEAT. 
a.   RADIATION. 

EXPERIMENT  91.     (At  home.) 

Hold  your  hand  for  a  few  seconds  near  a  hot  stove 
or  any  heated  body. 

Obs.   Observe  the  effect  upon  it. 
Inf.   Infer  the  cause  of  this. 

EXPERIMENT  92.      (At  home.) 

Obs.  Hold  the  hand  in  various  directions  from  the 
heated  body,  and  observe  the  effect. 

Inf.  Infer  in  what  directions  heat  passes  from 
heated  bodies. 

EXPERIMENT  93.      (At  hpme.) 

Obs.  Placing  the  hand  in  the  same  positions  as  be- 
fore, hold  a  sheet  of  paper  between  it  and  the  heated 
body,  and  observe  the  result. 

Inf.  1.  Infer  in  what  kind  of  lines  heat  passe: 
from  heated  bodies. 


HEAT.  95 

Inf.  2.  Call  this  passage  of  heat  from  a  heated 
body  radiation. 

Derive  the  term. 

Call  the  body  from  which  it  passes  a  radiator. 

Derive  radiator. 

Describe  the  use  of  fire  screens. 

XOTE.  —  Some  pupils  may  investigate  the  radiating  powers  of  rough 
and  smooth  surfaces. 

b.   CONDUCTION. 

EXPERIMENT  94.     (At  school.) 

To  a  small  iron  rod  about  16  inches  long  stick  4  or 
5  marbles  along  one  side  with  wax,  placing  one  3 
inches  from  the  end,  and  the  others  at  intervals  of 
2  or  3  inches. 

Hold  the  end  of  the  rod  in  the  flame  as  long  as  any 
of  the  marbles  stick 

01)s.    State  the  result. 

Inf.  1.    Infer  the  cause. 

Call  this  passage  of  heat  through  a  body  conduction. 

Derive  the  name. 

GOOD  AND  POOR  CONDUCTORS. 

EXPERIMENT  95.    (At  school.) 

Repeat  the  last  experiment,  using  a  slate  pencil  in 
place  of  the  iron  rod. 

Compare  the  rate  at  which  the  heat  passes  through 
the  pencil  with  that  at  which  it  passed  through  the 
iron  rod. 

Cc.11  the  pencil  a  poor  conductor,  and  the  rod  a  good 
^•conductor. 

Derive  conductor. 


96  ELEMENTARY  LESSONS  IN  PHYSICS. 

USES  OF  POOR  CONDUCTORS. 

EXPERIMENT  96.    (At  home.) 

Keep  a  block  of  oak  wood,  of  pine  wood,  and  of 
iron,  a  roll  of  cotton  cloth,  of  woollen  cloth,  and  of 
silk  cloth,  and  a  thermometer,  near  together  for  a  few 
hours  in  a  room  where  the  temperature  does  not 
change  much. 

Obs.  1.  Then  test  the  temperature  of  these  bodies 
with  the  thermometer,  keeping  it  on  each  for  a  few 
minutes. 

Obs.  2.  Touch  them  successively  to  the  cheek,  and 
see  if  they  all  feel  equally  warm. 

Inf.  1.   Infer  the  cause  of  the  differences. 

Inf.  2.    Why  is  clothing  necessary  ? 

Inf.  3.    What  is  the  best  material  for  clothing  ? 

1.   Mention  other  uses  of  poor  conductors. 

WATER  AS  A  CONDUCTOR. 

EXPERIMENT  97.    (At  school.) 

Take  a  test  tube  nearly  full  of  water,  and,  holding 
it  by  the  lower  part,  heat  it  just  below  the  surface 
of  the  water  until  the  water  begins  to  boil. 

Obs.  Observe  the  temperature  of  the  lower  part  of 
the  tube. 

Inf.    Infer  what  kind  of  a  conductor  water  is. 

Air  also  is  a  poor  conductor. 

What  use  is  made  of  this  fact  in  constructing 
houses  and  refrigerators  ? 


HEAT.  97 

WEIGHT  OF  HOT  AND  COLD  WATER. 

EXPERIMENT  98. 

Fill  a  small  can  with  cold  water,  and  balance  it  on 
a  scale  pan. 

Pour  out  the  cold  water  and  fill  with  hot. 

Obs.  Place  the  can  on  the  scale  pan,  and  compare 
its  weight  with  that  of  the  can  of  cold  water. 

Inf.    Infer  the  cause  of  this  difference. 

c.   CONVECTION. 

EXPERIMENT  99.    (At  home.) 

Take  a  cake  pan  two  thirds  full  of  water,  and  mix 
a  little  fine  sawdust  *with  it. 

Heat  it  gently  in  one  place  by  a  flame  below. 
Obs.    Observe  the  effect  in  the  water. 
Inf.  1.    How  can  you  explain  this  movement? 
Call  this  mode  of  distributing  heat  convection. 

Derive  convection. 

Inf.  2.    Explain  how  ocean  currents  are  produced. 

EXPERIMENT  10O.    (At  school.) 

Fit  a  broken  test  tube  about  4  inches  long  with  a 
stopper. 

Into  this  fit  a  piece  of  glass  tubing  (b  c  in  Figure 
37),  4  inches  long. 

Bend  another  piece  of  tubing,  15  inches  long,  as 
shown  in  Figure  37,  a  6,  and  fit  it  into  the  stopper  so 
that  it  will  reach  one  inch  above  the  other  tube. 

Connect  these  tubes  at  b  by  a  piece  of  rubber 
tubing. 


98 


ELEMENTARY   LESSONS  IN   PHYSICS. 


Set  a  crayon  box  upon  one  side,  and  place  another 
box  upon  this  in  the  same  position. 

Cut  slots  in  the  edges  of  these  boxes  for  the  tubes 
to  pass  through,  so  that  the  test  tube  may  rest  upon 
the  upper  box. 


Fig   37. 

Pour  water  slowly  into  the  test  tube  until  it  is 
nearly  filled,  and  add  a  little  fine  sawdust. 

Heat  the  slanting  portion  of  the  tube  with  a  candle 
flame. 

Obs.    Observe  any  movement  of  the  water. 

Inf.   Explain  what  causes  it. 


HEAT.  99 

1.  Explain  by  diagram  the  heating  of  buildings  ly 

hot  water. 

Some  pupil  may  construct  simple  hot-water  heating 
apparatus  of  glass  tubing. 

2.  Explain  by  diagram  ihe  furnishing  of  hot  water  in 

a  house  from  a  boiler  connected  with  kitchen 
range. 

Some  pupils  may  construct  simple  apparatus  illus- 
trating this  subject. 

DRAUGHTS. 

EXPERIMENT   1O1.     (At  home.) 

Hold  a  lamp  chimney  over  a  lamp  or  gas  flame  with 
the  left  hand,  and  with  the  right  hand  hold  a  strip 
of  very  thin  paper  one  quarter  of  an  inch  below  the 
level  of  the  bottom  of  the  chimney,  and  move  it  under 
the  chimney  on  the  same  level. 

06s.  1.    Is  the  paper  affected  ? 


Fig.  38. 


100  ELEMENTARY   LESSONS   IN   PHYSICS. 

Obs.  2.    In  the  same  way  hold  the  paper  over  the 
top  of  the  chimney  and  observe. 
Inf.    Explain  the  cause  of  this. 
Call  this  current  of  air  a  draught. 

EXPERIMENT    102.     (At  home.) 

Obs.  See  if  you  can  detect  any  draught  in  the  flue 
of  an  oil  stove,  by  testing  with  thin  paper  at  the  base 
and  at  the  top  of  the  flue. 

Inf.  1.    How  is  it  produced  ? 

Inf.  2.  Infer  the  cause  of  the  draught  through  a 
stove  and  up  the  chimney. 

1.  Describe  the  draught  about  a  hot  stove. 
Inf.  3.   Explain  how  it  is  caused. 

2.  Describe   heating   by  furnace,    representing   the 

furnace,   cold-air  box,  and  furnace  pipes  by 
diagram. 

WINDS. 

EXPERIMENT   103.     (At  home.) 

Hold  a  lighted  match  at  the  top,  and  then  at  the 
bottom,  of  a  doorway  between  a  warm  and  a  cool 
room. 

Obs.  Observe  the  direction  in  which  the  flame 
points  in  each  position. 

Inf.  1.   Infer  the  cause. 

Inf.  2.    Infer  how  these  draughts  are  produced. 

Inf.  3.    Infer  how  winds  are  produced. 

Inf.  4.    Explain  the  cause  of  land  and  sea  breezes. 

Inf.  5.   Explain  the  cause  of  the  trade  winds. 


HEAT. 


101 


4   LATENT   HEAT. 

EXPERIMENT  104-     (At  school.) 

Half  fill  a  small  flask  with  water. 

Insert  a  chemical  thermometer,  and  heat  the  water 
to  the  boiling  point. 

Obs.  1.    Note  the  temperature. 

Obs.  2.  Boil  2  or  3  minutes,  and  see  if  the  temper- 
ature rises  after  it  gets  to  boiling. 

Inf.  1.    Infer  what  becomes  of  the  heat  applied. 

Call  it  latent  heat. 

Derive  latent. 

EXPERIMENT   1O5.     (At  school.) 

Transfer  the  thermometer  to  a  can  containing  two 
or  three  times  as  much  cold  water  as  the  flask. 


Close  the  flask  with  a  perforated  stopper  into  which 
has  been  fitted  tight  a  bent  glass  tube  reaching  over 
into  the  can  of  water. 

Boil  the  water  in  the  flask  5  minutes. 


102  ELEMENTARY  LESSONS  IN  PHYSICS. 

Obs.  1.  Observe  the  quantity  of  water  in  the  flask 
and  in  the  can,  and  the  temperature  of  the  water  in 
the  can. 

Do  you  think  the  water  in  the  flask  has  been 
growing  hotter  ? 

Obs.  2.    Open  the  flask,  and  test  it. 

Inf.  1.    What  became  of  the  heat  applied  ? 

Inf.  2.    What  became  of  the  vapor  formed  ? 

Inf.  3.  What  became  of  the  latent  heat  when  this 
vapor  was  condensed  ? 

Inf.  4.  Explain  by  diagram  the  process  of  heating 
by  steam. 

Some  pupils  may  construct  apparatus  illustrating 
this  subject. 

EXPERIMENT  1O6.     (At  school.) 

In  one  test  tube  place  some  fine  ice  or  snow,  and  in 
another  an  equal  weight  of  water. 

Obs.  1.   Notice  the  temperature  of  each. 

Obs.  2.  Insert  both  in  a  can  of  hot  water  until  the 
ice  is  nearly  melted,  and  observe  the  temperature  of 
each. 

Inf.  1.    Infer  the  cause  of  the  difference. 

Inf.  2.  If  no  heat  were  absorbed  as  latent  heat  in 
melting,  how  long  would  it  take  the  deepest  snow  or 
the  thickest  ice  to  melt  ? 

Make  a  topical  outline  of  these  lessons  on  heat. 

Write  upon  some  of  the  topics. 


FRICTIONAL  OR  STATIC  ELECTRICITY.  109 

b    BALANCED  BAR. 

By  heating  soften  one  end  of  a  piece  of  sealing  wax 
about  2  inches  long,  and  stick  it  upright  upon  the  cen- 
tre of  a  tin  box-cover  2  or  3  inches  in  diameter. 

Heat  the  eye  of  a  needle,  and  insert  it  upright  in 
the  top  of  the  sealing  wax. 

With  sealing  wax,  stick  a  triangular  bit  of  tinfoil 
on  each  end  of  a  curved  splinter  of  wood  about  6 
inches  long,  and  balance  it  on  the  point  of  the  needle. 


Fig.  44. 

Use  this  balanced  bar  as  an  electroscope ;  i.  e.  to 
indicate  the  presence  of  electricity. 

EXPERIMENT  118.    (At  home.) 

Obs.  Excite  the  lamp  chimney  and  bring  it  near 
one  end  of  the  balanced  bar,  and  observe  the  effect. 

3.   KINDS. 

EXPERIMENT  119.     (At  school.) 

Obs.  1.  Excite  the  lamp  chimney  and  hold  it  near 
the  pith-balls  for  two  or  three  minutes,  and  observe 
what  happens. 

Obs.  2.    Try  the  same  with  the  sealing  wax. 


HO  ELEMENTARY  LESSONS  IN  PHYSICS. 

EXPERIMENT   120. 

Let  one  pupil  excite  the  lamp  chimney  and  another 
the  sealing  wax,  and  hold  them  for  a  minute  or  two 
about  an  inch  apart,  with  the  pith-balls  between  them. 

Obs.    Observe  what  happens. 

Inf.  How  can  you  account  for  this  action  of  the 
pith-balls  ? 

EXPERIMENT   181. 

Repeat  the  last  two  experiments,  using  the  balanced 
bar  instead  of  the  pith-balls. 

Call  the  electricity  excited  in  the  lamp  chimney 
positive  (-f),  and  that  excited  in  the  sealing  wax 
negative  (—). 

EXPERIMENT   128. 

Find  what  kind  of  electricity  is  excited  in  the  silk 
pad,  and  what  kind  in  the  flannel  pad. 

4.  LAW. 

EXPERIMENT   123. 

Bend  a  wire  12  inches  long  into  the  shape  shown 
in  Figure  45,  and  suspend  it  by  a  silk  thread. 


Fig.  45. 


FRICTIONAL  OR   STATIC   ELECTRICITY.  HI 

Let  one  pupil  excite  a  lamp  chimney  and  another  a 
second  one. 

Obs.  1.  Lay  one  of  the  chimneys  upon  the  wire 
hooks,  bring  the  other  near  one  end  of  this,  and 
observe  the  effect. 

Obs.  2.  Repeat  this  experiment,  using  two  sticks 
of  sealing  wax  in  place  of  the  chimneys. 

Obs.  3.  Repeat,  using  one  chimney  and  one  stick 
of  sealing  wax,  and  observe  the  effect. 

Inf.  Infer  how  bodies  charged  with  the  same  kind 
of  electricity  affect  each  other,  and  how  those  charged 
with  unlike  electricities  affect  each  other. 


5.   CONDUCTION. 
CONDUCTORS  AND  INSULATORS. 

EXPERIMENT  1.24.     (At  school.) 

Lay  a  piece  of  glass  tubing  1  foot  long  across  the  top 
of  a  tumbler  so  that  one  end  of  it  will  come  within 
about  one  eighth  of  an  inch  of  one  end  of  the  balanced 
bar. 

06s.  1.  Touch  the  excited  chimney  to  the  end  of 
the  tube  remote  from  the  electroscope,  and  see  if  the 
bar  is  affected. 

Obs.  2.  Try  the  excited  sealing  wax  in  place  of  the 
chimney. 

EXPERIMENT  185.     (At  school.) 

Repeat  Experiment  124,  using  a  hard-wood  foot  rule 
in  place  of  the  glass  tube. 


112  ELEMENTARY  LESSONS  IN   PHYSICS. 

EXPERIMENT  126.     (At  school.? 

Repeat,  using  your  lead  pencil. 

Repeat  again,  using  a  key. 

Inf.  1.  Infer  an  explanation  of  the  facts  observed 
in  Experiments  124  to  126. 

Call  the  action  of  electricity  over  a  body  con- 
duction. 

Call  a  body  over  which  electricity  acts  a  conductor, 
and  one  over  which  it  does  not  act  an  insulator. 

Derive  these  terms. 

Name  the  conductors  and  insulators  which  you 
have  found  in  these  experiments. 

Inf.  2.  Infer  why  glass  bottles  are  used  in  the 
electroscopes. 

Inf.  3.  Infer  why  the  pith-balls  fly  off  after  con- 
tact with  an  electrified  body,  and  why  they  repel 
each  other. 

Inf.  4.    Infer  the  use  of  lightning  rods. 

6.   INDUCTION.1 

EXPERIMENT  127.     (At  home.) 

Support  a  cylindrical  tin  box,  or  can,  with  the 
cover  on,  horizontally  upon  a  dry  tumbler,  so  that 
one  end  of  the  can  will  be  within  a  quarter  of  an 
inch  of  the  bar  electroscope. 

Bring  the  excited  chimney  or  sealing  wax  near  the 
Other  end  of  the  can,  without  contact. 

Obs.   Observe  the  effect  upon  the  electroscope. 

l  It  may  be  best  to  omit  this  topic  with  classes  in  grammar  schools. 


FRICTION AL  OR  STATIC   ELECTRICITY.  113 

Inf.    Infer  how  this  effect  can  be  produced. 

Call  the  development  of  electricity  in  a  body  by  the 
approach  of  an  electrified  body,  without  its  coming 
near  enough  for  a  spark  to  pass,  induction. 

Derive  the  term. 

See  what  other  bodies  you  can  induce  electricity  in. 

See  if  you  can  decide  what  kind  of  electricity  is 
manifest  on  the  end  of  the  can  toward  the  elec- 
troscope. (Recall  Experiment  123.) 

Obs.  and  Inf.  2.  Is  there  any  electricity  at  the 
other  end? 

Obs.  and  Inf.  3.    Of  what  kind  is  it  ? 

Inf.  4,  Infer  the  first  effect  of  bringing  an  excited 
body  near  an  insulated  body. 

Inf.  5.  In  view  of  this,  infer  why  the  pith-balls  and 
the  bar  are  attracted  to  an  excited  body. 


U4  ELEMENTARY  LESSONS  IN  PHYSICS. 

XI.    VOLTAIC  OR  CURRENT  ELECTRICITY. 
1.   VOLTAIC   ELEMENT. 

EXPERIMENT  188. 

Repeat  Experiment  20. 

Call  this  apparatus  a  Voltaic  element. 

1.  What  does  it  consist  of? 

2.   HOW  PRODUCED. 

Inf.  Infer  how  the  electricity  was  produced  in  the 
above  experiment. 

3.   EFFECTS. 

The  effects  and  applications  of  electricity  are  too 
numerous  and  varied  to  be  considered,  even  in  the 
briefest  way,  in  these  Lessons.  They  form  a  subject 
for  investigation  in  the  latter  part  of  the  High  School 
course. 

But  we  will  recall  briefly  two  or  three  effects  which 
we  have  already  noticed. 

a.    MAGNETIC. 

1.   What    effect   of   Voltaic    electricity    have   you 
already  observed? 


VOLTAIC  OR  CURRENT  ELECTRICITY.  115 


EXPERIMENT   129.     (At  school.) 

Wind  about  30  feet  of  insulated  No.  22  copper  wire 
around  a  small  rod  of  soft  iron  5  or  6  inches  long, 
and  connect  the  ends  with  the  plates  of  the  Voltaic 
element. 


Fig.  46. 

Obs.  1.  Bring  bits  of  iron  near  one  end  of  the  iron 
rod,  and  observe  the  effect. 

Obs.  2.  Bring  them  near  the  other  end,  and  ob- 
serve. 

Inf.  1.   Infer  what  the  rod  has  become. 

Inf.  2.    Infer  how  this  change  was  produced. 

Obs.  3.  Separate  one  end  of  the  wire  from  the 
plate,  and  see  if  the  rod  retains  its  magnetism. 

Obs.  4.  Hold  the  end  of  the  wire  to  the  plate,  and 
see  if  the  rod  is  now  a  magnet. 

Obs.  5.  Touch  a  very  small  tack  to  the  rod,  sepa- 
rate the  wire  from  the  plate,  and  see  how  long  the 
tack  is  held. 


116  ELEMENTARY   LESSONS   IN   PHYSICS. 

Inf.  3.    How  long  does  the  rod  continue  a  magnet 
after  the  connection  between  the  plates  is  broken  ? 
Call  the  iron  rod  an  electro-magnet. 

Pupils  are  now  prepared  to  examine  and  describe  the  key  and  receiver 
of  the  telegraph,  and  the  electric  bell  and  press-button. 

The  key  and  press-button  are  used  to  make  and  break  connections  ; 
and  the  receiver,  or  sounder,  and  the  "  bell "  are  applications  of  electro- 


The  construction  and  working  of  the  telegraph  and  the  electric  bell 
may  be  described  by  the  pupils  in  writing. 

1.    What  two  effects  of  Voltaic  electricity  have  you 
learned  ? 

b.   THERMAL. 

EXPERIMENT   13O.      (At  school.) 

Cut  the  connecting  wire  of  a  Grenet  battery,  and 
tvvist  around  the  ends  a  piece  of  fine  platinum  wire  so 
that  there  will  be  about  one  inch  of  it  between  the 
ends  of  the  copper  wire. 

Obs.  Lower  the  zinc  plate,  and  test  the  temperature 
of  the  platinum  wire. 

Inf.  Infer  how  the  change  has  been  produced. 

c.    LUMINOUS. 

1.  How  are  incandescent  electric  lights  produced  ? 

2.  What  other  luminous  effects  of  electricity  have 

you  noticed? 

Prepare  a  topical  outline  of  these  lessons  in  Elec- 
tricity, and  write  upon  some  of  the  topics. 


SOUND.  117 

XII.    SOUND. 

1.    HOW   PRODUCED. 

EXPERIMENT  131.      (At  home.) 

Strike  one  tine  of  a  pitchfork  a  sharp  blow,  not  too 
hard. 

Obs.  Notice  what  the  tine  does,  and  what  you 
hear. 

EXPERIMENT   133. 

Obs.  Pull  a  piano  string  a  little  to  one  side,  let  it 
go,  and  observe  as  in  the  last  experiment. 

EXPERIMENT  133. 

Strike  a  call  bell,  and  hold  a  pencil  lightly  against 
one  edge  of  the  bell. 

Obs.   Observe  the  effect  as  before. 


Fig.  47. 

Inf.  1.    Infer  why  the  pencil  moves. 
Inf.  2.    From  these  experiments  infer  what  sound 
is  due  to. 


ELEMENTARY  LESSONS  IN  PHYSICS, 


2.   TRANSMISSION  OF  VIBRATIONS, 
a.  THROUGH   WOOD. 

EXPERIMENT   134.    (At  home.) 

Hold  a  lath  horizontal,  with  one  end  resting  lightly 
against  the  panel  of  a  door. 

Make  a  tuning-fork  vibrate,  and  press  the  end  of 
its  handle  against  the  free  end  of  the  lath.  (A  steel 
table-fork  will  do.) 

Obs.   Observe  where  the  sound  seems  to  come  from. 

Inf.   Infer  how  the  vibrations  reached  the  door. 

6.  THROUGH   A  STRING. 

EXPERIMENT   135.    (At  home.) 

Punch  a  little  hole  through  the  centre  of  the  cover 
and  bottom  of  a  cylindrical  tin  box. 

From  the  outside  insert  one  end  of  a  string  10  or 
12  feet  long  through  the  hole  in  the  cover,  and 
the  other  end  through  the  hole  in  the  bottom.  Tie 
knots  in  the  ends  to  keep  them  from  pulling  out. 
Let  one  person  hold  the  open  end  of  the  box  to  his 
ear,  and  another  person  hold  the  cover  far  enough 
away  to  straighten  the  string,  and  sounding  the 
tuning-fork  (or  table-fork),  touch  the  handle  to  the 
box  cover. 

Obs.  1.  The  one  holding  the  box  to  the  ear  report 
the  effect. 

Obs.  2.    Where  did  the  sound  seem  to  come  from  ? 

Inf.   Infer  how  the  vibrations  reached  the  box. 


SOUND.  119 

c.   THROUGH   THE   AIR. 

EXPERIMENT   136.    (At  home.) 

Lay  a  piece  of  writing  paper  over  the  mouth  of  a 
tumbler,  leaving  an  opening  half  an  inch  or  less  in 
width,  and  trim  off  the  outside  of  the  paper  so  that 
it  will  not  project  more  than  half  an  inch  beyond 
the  edge  of  the  tumbler. 

Press  the  paper  down  against  the  tumbler,  and 
sprinkle  a  little  fine  sand  on  it. 

Obs.  Sing  a  strong,  full  tone,  and,  slowly  raising 
and  lowering  the  pitch,  watch  the  sand  upon  the 
paper. 

If  the  sand  is  not  affected,  change  the  size  of  the 
opening  slightly,  and  repeat  until  it  is  affected. 

Inf.  1.    Infer  how  this  effect  is  produced. 

Inf.  2.    Infer  how  the  vibrations  reached  the  paper. 

In  the  ear  is  a  little  membrane,  stretched  over  a 
bony  framework,  and  forming  the  "  drum "  of  the 
ear,  with  which  the  air  comes  in  contact. 

Inf.  3.  Infer  how  it  will  be  affected  when  objects 
near  us  are  made  to  vibrate. 

These  vibrations  continuing,  reach  the  auditory 
nerve,  and  the  sound  is  heard. 

1.  What  have  you  observed  that  would  indicate  at 
what  rate  sound  is  transmitted  through  air? 

Plan  an  experiment  which  will  show  approximately 
the  velocity  of  sound  in  air. 


120  ELEMENTARY  LESSONS  IN   PHYSICS. 

3.   VIBRATING  STRINGS, 
a.   LOUDNESS   OF   TONES. 

EXPERIMENT  137.     (At  school.) 

Stretch  a  violin  string  over  a  sonometer. 

Derive  sonometer. 

With  the  finger  press  the  string  a  little  to  one  side, 
and  then  let  it  slip. 

Obs.  1.    Observe  the  effect. 

Press  the  string  farther  to  one  side,  and  let  it  slip. 


Fig.  48. 


Obs.  2.    Notice  the  distance  which  the  string  vi- 
brates, and  the  loudness  of  the  tone. 

Obs.  3.   Press  the  string  still  farther,  and  observe. 


SOUND.  121 

Call  the  distance  through  which  particles  vibrate 
the  amplitude  of  vibration. 

Derive  amplitude. 

Inf.  Infer  what  the  loudness  of  a  tone  depends  upon. 

Any  strong  string  rubbed  with  beeswax  will  do  for  these  experiments. 

If  a  sonometer  cannot  readily  be  procured,  get  a  soap-box  with  a 
thin,  close  bottom  (Ivory-soap  boxes  are  good),  and  invert  it  upon  a 
table. 

Ipsert  a  screw  in  the  middle  of  one  end,  and  a  pulley  in  the  middle 
of  the  other  end. 

On  the  top  of  the  box  above  the  screw  fasten  a  block,  cut  so  that 
the  inner  edge  will  be  a  little  higher  than  the  outer  edge,  as  shown  in 
Figure  48. 

Make  another  block  in  the  form  of  a  triangular  prism,  so  that  when 
laid  upon  one  side  it  will  be  1  inch  or  more  in  height. 

Fasten  one  end  of  the  string  to  the  screw,  and  pass  the  other  end 
over  the  pulley. 

The  string  may  be  stretched  by  the  hand  or  by  weights. 

b.   PITCH  OF  TONES. 

EXPERIMENT   138.      (At  school.) 

Stretch  a  lighter  or  a  heavier  string  than  was  used 
in  the  last  experiment  with  the  same  force  (weight), 
and  repeat  the  experiment. 

1.  Compare  the  tone  of  this  string  with  that  of  the 
other. 

Inf.  Infer  whether  light  strings  or  heavy  ones 
give  higher  tones. 

EXPERIMENT   139.     (At  school.) 

Obs.  Place  the  movable  block  at  the  end  next  to 
the  pulley,  stretch  the  string  with  a  weight,  sound  the 
string,  and  notice  the  pitch  of  its  tone. 


122  ELEMENTARY  LESSONS  IN  PHYSICS. 

Move  the  block  inward  so  as  to  shorten  the  vibrat- 
ing string,  and  repeat  the  experiment. 

1.  Compare  the  pitch  of  the  tone  with  that  of  the 

tone  of  the  longer  string. 

2.  Shorten  the  vibrating  string  more,  and  repeat 

the  experiment. 

Inf.  Infer  how  the  tone  is  affected  by  the  length 
of  the  string. 

EXPERIMENT   140.     (At  school.) 

Sound  a  string  16  inches  long,  and  then  one  8  inches 
long  and  stretched  with  the  same  force. 
Compare  the  tones. 

EXPERIMENT   141.     (At  school.) 

Stretch  a  string  slightly  with  the  hand. 

01)s.  1.    Sound  it,  and  observe  its  pitch. 

Obs.  2.  Stretch  it  a  little  harder,  and  repeat  the 
experiment. 

Obs.  3.    Stretch  it  still  harder,  and  repeat. 

Inf.  Infer  how  the  tone  is  affected  by  increasing 
the  stretching  force  of  the  string. 

EXPERIMENT   143.    (At  school.) 

Stretch  a  string  8  or  10  inches  long  with  a  force  of 
1  pound. 

Sound  the  string,  and  note  its  pitch. 

Stretch  the  string  with  a  weight  of  4  pounds,  and 
repeat. 

1.    Compare  the  pitches  of  these  tones. 


SOUND.  123 

2.  What  three  things  have  we  learned  affect  the 

pitch  of  tones  produced  by  vibrating  strings  ? 

3.  What  strings  give  high  tones  ? 

4.  What  strings  give  low  tones  ? 

5.  How  are  the  strings  of  a  piano  varied  to  produce 

the  different  tones  desired  ?  ' 

6.  How  are  pianos  tuned  ? 

Repeat  experiments  139-142,  noticing  carefully  the  rate  of  vibration 
in  each  case,  and  see  if  you  can  decide  what  the  pitch  of  a  tone  really 
depends  upon. 

4.   VIBKATING  COLUMNS  OF  AIR 

EXPERIMENT   143.     (At  school.) 

Get  or  make  an  organ-pipe  with  one  glass  side,  a  b, 
as  shown  in  Figure  50. 

An  organ-pipe  may  be  made  from  a  straight  lamp 
chimney,  by  filing  a  hole  at  the  lip,  I,  as  shown  in 
Figure  49. 


Fig.  49 

But  great  care  is  necessary  to  get  it  tight  and  not 
break  the  chimney. 

Obs.  Blow  in  at  the  mouthpiece,  and  observe  the 
effect. 

EXPERIMENT   144.    (At  school.) 

Draw  a  piece  of  rubber  tubing  from  16  to  24  inches 
long  over  the  mouthpiece. 

Cut  out  a  piece  of  writing  paper  a  little  smaller 


124 


ELEMENTARY  LESSONS  IN   PHYSICS. 


I , 


T  \3 

Fig.  50.  — ORGAN  PIPE. 


Fig   51. 


than  the  interior  of  a  cross  section  of  the  organ-pipe, 
and  suspend  it  by  a  thread. 

Scatter  a  little  fine  sand  upon  the  paper,  and,  hold- 
ing the  pipe  vertically  with  the  open  end  upward,  so 
that  you  can  see  through  the  glass  side,  sound  the 
organ-pipe  by  blowing  through  the  rubber  tube. 

Slowly  lower  the  sanded  paper  into  the  sounding 
pipe,  and  carefully  watch  the  sand. 

Obs.   What  do  you  observe  ? 

Inf.  Infer  the  cause. 

As  the  air  is  forced  into  the  organ-pipe,  it  strikes  the  lip  (I,  Figure 
50),  and  thus  obstructed,  it  issues  from  the  opening  in  rapid  puffs. 
The  pulsations,  thus  produced,  are  transmitted  to  the  column  of  ail 
within  the  pipe,  and  cause  it  to  vibrate. 


SOUND.  125 

EXPERIMENT  145.    (At  home.) 

Blow  across  the  mouth  of  a  small  bottle  so  as  to 
produce  a  tone,  and  notice  its  pitch. 

EXPERIMENT   146.    (At  home.) 

Blow  across  the  mouth  of  a  larger  bottle,  and  com- 
pare the  pitch  of  its  tone  with  that  of  the  tone  of 
the  smaller  bottle. 

EXPERIMENT  147.    (At  home.) 

Obs.  1.  Pour  a  little  water  into  the  larger  bottle, 
"sound"  it,  and  compare  its  tone  with  that  of  the 
"empty"  bottle. 

Obs.  2.  Add  more  water,  and  observe  how  the  tone 
changes. 

Inf.  Infer  how  the  tone  of  an  organ-pipe  is  affected 
by  the  length  of  the  pipe. 

EXPERIMENT   148.    (At  school.) 

Obs.  Close  the  outer  end  of  the  organ-pipe  air- 
tight, sound  it,  and  compare  its  tone  with  that  of 
the  open  pipe. 

Inf.  Infer  what  kind  of  organ-pipes  produce  high 
tones,  and  what  kind  produce  low  tones. 

Write  a  composition  upon  the  pitch  of  tones,  de- 
ducing the  facts  from  experiments. 

Make  a  topical  outline  of  the  lessons  on  sound. 


ELEMENTARY  LESSONS  IN  PHYSICS. 


XHI.    LIGHT. 

1.     SOUKCES. 

Name  some  bodies  which  originate  light. 
Call  such  bodies  luminous  bodies. 

Derive  luminous. 

Mention  some  bodies  which  do  not  originate  light. 
Call  such  bodies  non-luminous  bodies. 

Derive  non-luminous. 

Call  a  body  which  receives  light  from  other  bodies 
xnd  reflects  it  an  illuminated  body. 

Derive  the  terra. 

1.  All  light  comes  originally  from  what  kind  of 

bodies  ? 

2.  Name  the  natural  sources  of  light. 

3.  Name  the  chief  artificial  sources  of  light. 

The  profitable  study  of  light  requires  a  porte  lumiere  and  arrange- 
ments for  darkening  the  room. 

The  windows  may  be  darkened  by  wide  curtains  of  dark  cambric, 
pinned  close  over  the  window-frames,  or  by  shutters  made  by  tacking 
strong  opaque  paper  over  wooden  frames  made  to  fit  the  window-frames. 

A  porte  lumiere  may  be  bought  for  about  $5.00 ;  or  one  suitable  for 
these  experiments  may  be  made  at  an  expense  of  about  $0.50. 

To  MAKE  A  PORTE  LUMIERE. 

Get  a  piece  of  pine  board  9  inches  wide,  and  as  long  as  the  width  of 
a  window  on  the  south  side  of  the  school-room. 

On  one  side  of  this  board  mark  out  a  circle  6  incV.es  in  diameter, 
with  its  centre  |  inch  above  the  central  point  of  the  board. 

Saw  it  out  with  a  compass-saw  as  marked. 


LIGHT. 


127 


128  ELEMENTARY  LESSONS  IN  PHYSICS. 

If  necessary,  even  the  edge  of  this  circular  piece  so  that  it  will  turn 
as  a  wheel  in  the  hole. 

In  the  centre  of  this  wheel  bore  or  cut  a  round  hole  2  inches  in 
diameter. 

From  |  inch  board  cut  a  ring  (R,  Figure  52)  7  inches  in  diameter 
on  the  outside  and  4  inches  inside. 

With  1|  inch  wire  nails  fasten  this  ring  to  one  side  of  the  wheel,  so 
that  its  rim  will  project  beyond  the  rim  of  the  wheel  £  inch  all  round. 

Cut  out  a  piece  of  pine  board  4  X  8  inches  (M,  Figure  52). 

To  one  side  of  this  fasten  a  piece  of  looking-glass,  3|  X  7£  inches, 
by  small  screws,  placed  so  their  heads  will  lap  over  the  edge  of  the 
looking-glass 

With  a  suitable  hinge  and  rather  long  screws  hang  this  mirror  to 
the  wheel  in  the  position  shown  in  Figure  52,  so  that  the  mirror  may 
be  raised  against  the  wheel. 

In  one  edge  of  the  mirror.  3|  inches  from  the  wheel,  insert  a  small 
screw  (S),  letting  the  head  project. 

Raise  the  mirror  against  the  wheel,  and  with  a  brad  awl  make  a 
hole  (H)  through  the  wheel  opposite  the  screw  in  the  edge  of  the 
mirror. 

To  the  screw  fasten  one  end  of  a  string  about  18  inches  long,  and 
pass  the  other  end  through  the  awl  hole. 

Upon  the  ring,  a  little  below  and  at  the  right  of  the  awl  hole,  by 
means  of  screws  fasten  a  small  cleat  (c)  to  hitch  the  string  to.  Thus 
the  mirror  may  be  held  at  any  angle  desired. 

Of  hard  wood  make  two  buttons  (B,  B)  about  H  X  |  X  i  inch, 
and  fasten  each  with  a  screw  to  the  wheel,  as  shown  in  the  figure. 

Turn  these  buttons  so  that  they  will  not  project  beyond  the  rim  of 
the  wheel,  place  the  wheel  in  the  board,  and  fasten  it  by  turning  the 
buttons. 

Place  the  porle  lumiere  under  the  lower  sash  of  a  window  on  the 
sunny  side  of  the  room,  and  adjust  it  —  by  turning  the  wheel  and 
increasing  or  diminishing  the  angle  of  the  mirror  —  so  that  it  will 
throw  the  light  squarely  and  horizontally  into  the  room. 

For  experiments  with  small  lenses  a  smaller  opening  for  the  admis- 
sion of  light  may  be  needed  A  hole  of  the  right  size  may  be  cut  in 
a  piece  of  cardboard  and  the  cardboard  tacked  or  pinned  over  the 
hole  in  the  wheel. 

Derive  porle  lumilre. 


LIGHT.  129 

2.     TRANSMISSION. 
a.  MEDIUM,  — TRANSPARENT;    TRANSLUCENT. 

EXPERIMENT  149.    (At  school.) 

With  a  porte  luraiere  throw  some  sunlight  into  a 
darkened  room. 

Obs.   Can  you  see  the  light  ? 

Call  that  through  which  it  passes  a  medium. 

Derive  the  term. 

EXPERIMENT  ISO.    (At  school.) 

Obs.  Hold  a  piece  of  window-glass  in  the  path  of 
the  light,  and  observe  how  much  of  the  light  passes 
through  the  glass. 

1.   How  much  of  it  passes  through  the  air? 

Call  the  glass  and  the  air  transparent  media. 

Derive  transparent. 

EXPERIMENT  151.    (At  school.) 

Obs.  Place  colored  glass,  also  thin  paper,  in  the 
path  of  the  light,  and  observe  how  much  light  passes 
through. 

Call  such  bodies  as  the  colored  glass  and  thin  paper 
translucent  media. 

Derive  translucent. 

1.  Name  other  transparent  media. 

2.  Name  other  translucent  media. 

3.  How  much  light  will  pass  through  a  piece  of 

inch  board  or  a  book? 
Call  these  opaque  bodies. 

Derive  opaque. 

i 


130  ELEMENTARY   LESSONS   IN   PHYSICS. 

6.   RAY;  c.  BEAM. 

EXPERIMENT   158.    (At  school.) 

Strike  together  two  erasers  containing  crayon  dust 
along  the  path  of  light. 

Obs.  1.  Observe  in  what  kind  of  lines  the  light 
passes. 

Call  a  single  line  of  light  a  ray. 

Derive  the  term. 

1.   Are  there  many  or  few  rays  of  light  thrown  into 

the  room  by  the  porte  lumiere  ? 
Obs.  2.    How  do  these  rays  compare  in  direction  ? 
Call  a  collection  of  parallel  rays  a  beam  of  light. 

d.  PENCIL  OF  LIGHT. 

EXPERIMENT   153.    (At  school.) 

Place  a  double  convex  lens  (see  page  139)  in  the 
beam  of  light,  and  render  the  path  of  rays  beyond 
the  lens  visible  by  crayon  dust. 

Obs.  Observe  the  relative  direction  of  the  rays  be- 
yond the  lens. 

Call  a  collection  of  rays  converging  to  the  same 
point  or  diverging  from  the  same  point  a  pencil  of 
light. 

The  first  is  called  a  converging  pencil. 

The  second  is  called  a  diverging  pencil. 

Derive  pencil,  converging  and  diverging. 


LIGHT.  131 

e.    IMAGE  BY  SMALL  APERTURE. 

EXPERIMENT  154.    (At  school.) 

Bore  a  hole  about  half  an  inch  in  diameter  in  one 
end  of  a  soap-box  without  cracks,  and  cover  the  hole 
with  a  piece  of  tinfoil. 

Prick  a  hole  in  the  tinfoil  with  a  pin. 

Invert  the  box  over  a  lighted  candle  in  a  darkened 
room,  and  hold  a  sheet  of  white  paper  as  a  screen  be- 
fore the  hole  in  the  tinfoil. 

Obs.  1.    Observe  what  forms  on  the  screen. 

Inf.  1.  See  if  you  can  think  out  and  show  by  dia- 
gram how  this  is  formed. 

Obs.  2.  Bringing  the  screen  near  the  box,  and 
removing  it  gradually,  observe  the  effect  upon  the 
image. 

Inf.  2.  See  if  you  can  explain  the  effect  by  dia- 
gram. 

EXPERIMENT   155      (At  school.) 

Through  a  hole  from  J  to  f  of  an  inch  in  diameter 
admit  light  from  without  into  a  darkened  room,  and 
have  a  large  screen  or  light  wall  on  the  side  of  the 
room  opposite  the  hole. 

Obs.   Observe  the  result. 

/.  SHADOW,  UMBRA,  AND  PENUMBRA. 

EXPERIMENT  156.     (At  home.) 

Before  a  lamp  flame  in  a  darkened  room  hold  an 
opaque  body  smaller  than  the  flame. 

Hold  a  white  screen  (paper)  just  beyond  the  opaque 
body,  and  gradually  move  it  farther  away. 


132  ELEMENTARY   LESSONS  IN   PHYSICS. 

Obs.    Observe  the  appearance  on  the  screen. 

Inf.  See  if  you  can  explain  the  appearance  by 
diagram. 

Call  the  space  from  which  light  is  shut  off  by  an 
opaque  body  a  shadow. 

Call  the  space  from  which  all  the  light  is  shut  off 
the  umbra. 

Call  the  space  from  which  a  part  only  is  shut  off 
the  penumbra. 

Derive  these  terms. 

g.   ECLIPSE  OF  THE  MOON. 

Is  the  moon  a  luminous  or  an  illuminated  body  ? 
Where  does  its  light  come  from  ? 
Is  the  earth  transparent  or  opaque  ? 
What  must  there  be  on  the  side  of  the  earth  away 
from  the  sun  ? 

Is  the  earth  larger  or  smaller  than  the  sun  ? 
What  must  be  the  form  of  the  earth's  umbra  ? 
What  must  be  the  form  of  the  earth's  penumbra? 
Explain  how  an  eclipse  of  the  moon  is  produced. 

h.   ECLIPSE  OF  THE   SUN. 

Describe  the  umbra  and  penumbra  of  the  moon. 
Explain  how  an  eclipse  of  the  sun  is  produced. 

i.    VELOCITY  OF  LIGHT. 

It  has   been   found    that    light   passes   across   the 
earth's  orbit  in  16  minutes  36  seconds. 


LIGHT.  133 

The  average  distance  of  the  earth  from  the  sun  is 
thought  to  be  about  93,000,000  miles. 

How  far  must  the  light  travel  in  a  second  ? 

j.    REFLECTION  OF  LIGHT. 

EXPERIMENT   157.     (At  school.) 

By  a  porte  lumiere  throw  a  beam  of  light  into  a 
darkened  room,  and  place  a  mirror  in  its  path. 

Render  the  path  of  the  -light  visible  by  crayon 
dust. 

Obs.  Observe  and  state  the  effect  of  the  mirror 
upon  the  light. 

Call  this  turning  back  rays  of  light  in  regular  order 
reflection. 

Derive  the  term. 

A  mirror  is  what  kind  of  a  surface  ? 
What  does  it  dc  with  light  ? 

LAW  OF  REFLECTION. 

Think  of  a  perpendicular  to  the  mirror  at  the  point 
where  the  light  strikes  the  mirror. 

Call  the  angle  which  the  rays  falling  upon  the  mir- 
ror make  with  this  perpendicular  the  angle  of  incidence. 

Derive  incidence. 

Call  the  angle  which  the  reflected  rays  make  with 
the  perpendicular  the  angle  of  reflection. 

Compare  the  angle  of  incidence  with  the  angle  of 
reflection. 


134  ELEMENTARY   LESSONS  IN   PHYSICS. 

DIFFUSED  LIGHT. 

EXPERIMENT   158.      (At  school.) 

Obs.  Place  a  piece  of  rough  paper  in  the  path  of 
the  rays,  and  see  if  the  light  is  reflected  regularly. 

Call  light  thus  scattered  by  a  rough  surface  diffused 
light. 

Derive  diffused. 

IMAGE  OF  A  POINT  BY  A  PLANE  MIRROR. 

EXPERIMENT  159.    (At  home.) 

Hold  the  point  of  your  pencil  in  front  of  a  plane 
mirror. 

Obs.  Observe  and  describe  the  location  of  the 
image  of  the  point,  as  seen  from  any  position. 

Is  the  image  in  front  of  the  mirror,  or  behind  it  ? 

How  far  ? 

Where  with  reference  to  a  line  perpendicular  to  the 
mirror  and  passing  through  the  point  of  the  pencil  ? 

IMAGE  OF  AN  OBJECT  BY  A  PLANE  MIRROR 

EXPERIMENT  160.     (At  home.) 

Hold  any  object  before  a  plane  mirror. 

Obs.  Observe  and  state  the  position  of  the  image 
of  each  point  of  the  object. 

When  you  look  in  a  mirror,  the  image  of  your  right 
eye  forms  which  eye  of  the  image  of  your  face  ? 

IMAGES  BY  Two  PARALLEL  PLANE  MIRRORS. 

EXPERIMENT   161.      (At  school.) 

Cut  out  a  piece  of  board  in  the  form  of  a  quadrant 
with  a  radius  of  10  inches. 


LIGHT. 


135 


Along  one  of  the  sides  saw  two  parallel  scaths 
(a  and  b  in  Figure  53)  J  of  an  inch  deep  and  4  inches 
apart ;  and  three  other  scaths  (<?,  d,  and  e  in  the 
figure),  making  angles  of  30,  60,  and  90  degrees  re- 
spectively with  the  scath  a. 

In  the  parallel  scaths  place  two  pieces  of  looking- 
glass,  2  by  6  inches,  facing  each  other. 


Fig.  53. 

Obs.  Place  a  piece  of  crayon  between  these  mirrors, 
and  see  if  you  can  see  more  than  one  image  of  it. 
How  many  ? 

Where  are  they  ? 

IMAGES  BY  Two  PLANE  MIRRORS  AT  AN  ANGLE. 

EXPERIMENT  163.      (At  school.) 

Obs.  On  the  same  board  arrange  the  mirrors  at 
angles  of  30,  60,  and  90  degrees,  and  find  how  many 
images  can  be  seen  from  one  position  with  the  mirrors 
at  each  of  these  angles 


136  ELEMENTARY   LESSONS   IN  PHSYICS. 

CONCAVE  MIRROR,  PRINCIPAL  Focus,  FOCAL  DISTANCE, 
CENTRE  OF  CURVATURE. 

EXPERIMENT    163.      (At  school.) 

Place  a  concave  mirror  in  the  path  of  a  beam 'of 
light  in  a  darkened  room,  so  that  the  light  will  strike 
perpendicularly  at  the  centre  of  the  mirror. 

Obs.  Render  the  path  of  the  reflected  light  visible 
by  crayon  dust,  and  describe  the  direction  of  the 
rays. 

Draw  a  diagram  showing  how  the  light  is  reflected. 

Call  the  point  through  which  all  the  reflected  rays 
pass  the  principal  focus  of  the  mirror. 

Derive  focus. 

Call  its  distance  from  the  mirror  the  focal  distance 
of  the  mirror. 

Call  the  point  directly  in  front  of  the  mirror  twice 
as  far  away  as  the  principal  focus  the  centre  of  curva- 
ture of  the  mirror. 

Inf.   Infer  why  it  is  so  called. 

IMAGE  BY  A  CONCAVE  MIRROR. 

EXPERIMENT   164.      (At  school.) 

In  a  darkened  room  place  a  lighted  candle  at  con- 
siderable distance  beyond  the  centre  of  curvature  and 
a  little  to  the  right  of  "it. 

Hold  a  piece  of  white  paper  as  a  screen  just  to  the 
left  of  the  principal  focns,  and  moving  it  slowly  away 
from  the  mirror,  see  if  the  image  of  the  candle  flame 
is  formed  on  it. 


LIGHT.  137 

Obs.  Describe  the  image.  (Erect  or  inverted  ? 
Where  with  reference  to  the  centre  of  curvature  ? 
How  large  compared  with  the  object  ?  ) 

EXPERIMENT  165.   (At  school.) 

Bring  the  candle  nearer  the  centre  of  curvature, 
and  find  and  describe  the  image. 

EXPERIMENT   166.     (At  school.) 

Obs.  Carry  the  candle  nearer  the  mirror  than  the 
centre  of  curvature,  and  find  and  describe  the  image. 

EXPERIMENT   167.     (At  school.) 

Obs.  See  if  any  image  is  formed  when  the  object 
is  located  at  the  principal  focus,  within  the  principal 
focus,  and  at  the  centre  of  curvature. 

Inf.    Infer  why  this  is  so. 


Fig.  54. 
k.   REFRACTION. 

EXPERIMENT   168.      (At  school.) 

By  means  of  a  mirror  (a)  throw  a  beam  of  light 
obliquely  into  colored  water,  and  render  the  path  of 
rays  through  the  air  visible  by  crayon  dust. 


138  ELEMENTARY  LESSONS  IN  PHYSICS. 

Hold  a  long  pencil,  or  straight  stick,  parallel  with 
the  beam  above  the  water,  so  that  the  under  side  of 
the  pencil  will  just  touch  the  beam  along  the  upper 
side,  and  let  the  lower  end  of  the  pencil  extend  down- 
ward to  the  bottom  of  the  water. 

Obs.  Do  the  rays  continue  parallel  with  the  pencil 
after  entering  the  water? 

Call  the  change  in  direction  refraction. 

Derive  the  term. 

EXPERIMENT   169.      (At  school.) 

Obs.  Throw  the  light  perpendicularly  into  the 
water,  and  see  if  there  is  any  refraction. 

DIRECTION  OF  THE  CHANGE. 

1.  Which  is  the  denser  medium,  air  or  water? 
Think  of   a   perpendicular   to   the  surface    of   the 

water  at  the  point  where  the  light  enters  the  water. 

2.  Is  the  light  bent  toward  this  perpendicular,  or 

away  from  it,  as  it  enters  the  water? 

3.  Under  what   conditions    have  you    found    that 

light  is  refracted,  and  in  what  direction  are 
the  rays  bent  ? 

EXPERIMENT   17O.     (At  home.) 

Place  a  cent  in  a  basin  just  near  enough  to  one  side 
so  that  you  cannot  see  it  with  the  eye  in  a  certain 
fixed  position. 

Without  changing  the  position  of  the  eye,  care- 
fully pour  in  on  the  farther  side  of  the  basin,  so 


LIGHT. 


139 


as  not  to  move  the  cent,  enough  water   to   nearly 
fill  the  basin'. 


Fig.  55. 

Obs.    Can  you  see  the  cent  now? 

Inf.  Infer  in  what  kind  of  a  line  the  light  must 
have  passed  from  the  cent  to  the  eye. 

Compare  the  direction  in  which  the  rays  are  bent 
on  leaving  the  water  with  the  direction  in  which  they 
were  bent  in  Experiment  167  on  entering  the  water. 

BY  A  DOUBLE-CONVEX  LENS. 

A  double-convex  lens  is  a  circular  glass  body  with 
its  sides  curved  out  so  as  to  make  it  thickest  in  the 
centre. 

A  section  of  it  is  shown  in  Figure  56. 


A 


V 

Fig.  56. 


140  ELEMENTARY  LESSONS  IN  PHYSICS. 

A  lens  3  or  4  inches  in  diameter  is  desirable  for 
these  experiments,  though  a  2-inch  lens  might 
answer. 

OF  PARALLEL  RAYS,  PRINCIPAL  Focus,  FOCAL  DISTANCE. 

EXPERIMENT   171.     (At  school.) 

In  a  darkened  room  place  a  double-convex  lens  in 
the  path  of  a  beam  of  light  so  that  the  light  will 
strike  the  lens  perpendicularly  at  its  centre. 

Render  the  path  of  the  light  visible. 

Obs.  Observe  and  state  how  it  passes  after  leaving 
the  lens. 

Call  the  point  through  which  all  the  refracted  light 
passes  the  principal  focus  of  the  lens. 

Inf.  What  would  you  call  its  distance  from  the 
lens? 

IMAGE  OF  AN  OBJECT. 

EXPERIMENT  173.      (At  school.) 

In  a  darkened  room  place  the  flame  of  a  candle 
just  beyond  the  principal  focus  of  a  double-convex 
lens. 

Obs.  Find  the  image  on  white  paper  on  the  other 
side  of  the  lens. 

Describe  the  image.  (How  far  away  compared  with 
the  object  ?  How  large  ?  Erect  or  inverted  ?) 

EXPERIMENT  173.     (At  school.) 

Increase  the  distance  of  the  flame  from  the  lens, 
and  tell  how  the  image  changes. 


LIGHT.  141 

How  far  is  the  flame  from  the  lens  when  the  image 
is  of  the  same  size  as  the  object? 

HUMAN  EYE. 

Describe  the  human  eye  and  explain  how  we  see. 
SIMPLE  MICROSCOPE. 

Look  through  a  double-convex  lens  at  an  object 
located  within  the  principal  focus. 

Describe  the  image  seen. 

Call  this  lens  a  simple  microscope. 

Sometimes  two  or  three  lenses  placed  near  together 
are  used  as  a  simple  microscope. 

Derive  the  term  microscope. 

COMPOUND  MICROSCOPE. 

EXPERIMENT   174.     (At  school.) 

In  a  darkened  room  place  a  candle  flame  just  be- 
yond the  principal  focus  of  a  small  double-convex 
lens. 

Find  the  image  of  the  flame. 

Place  a  larger  lens  just  beyond  the  image  made 
by  this  lens. 

Look  through  the  larger  lens  toward  the  flame. 

Describe  the  image  seen. 

EXPERIMENT   175.     (At  school.) 

In  a  light  room  substitute  any  small  object  for  the 
candle  flame,  and  observe  and  describe. 


142  ELEMENTARY  LESSONS  IN  PHYSICS. 

Call  this  combination  of  lenses  a  compound  micro- 
scope. 

REFRACTING  TELESCOPE. 

EXPERIMENT   176.     (At  school.) 

In  a  darkened  room  place  a  candle  flame  at  con- 
siderable distance  from  a  large  double-convex  lens. 

Just  beyond  the  image  formed  by  this  lens,  place 
a  small  lens. 

Look  through  the  small  lens  toward  the  flame, 
and  describe  the  image  seen. 

EXPERIMENT  177.     (At  school.) 

In  a  light  room  substitute  any  object  for  the  candle 
flame,  and  observe  and  describe  as  before. 

Call  this  combination  of  lenses  a  refracting  telescope. 

Derive  telescope. 

Tell  how  the  refracting  telescope  differs  from  the 
compound  microscope. 

REFRACTION  BY  A  PRISM.     SOLAR  SPECTRUM. 

EXPERIMENT   178.     (At  school.) 

Through  a  small  hole  admit  light  from  the  sun 
into  a  dark  room,  and  have  a  screen  or  white  wall 
in  the  path  of  the  light.  (Use  a  porte  lumiere.) 


Fig.  57, 


LIGHT.  113 

What  is  formed  on  the  screen  ? 
(See  Experiment  154.) 

EXPERIMENT   179.      (At  school.) 

Hold  a  glass  prism,  base  upward,  in  the  path  of  the 
beam  of  light. 

Observe  the  change  in  the  position,  form,  and  color 
of  the  image. 

Infer  the  causes  of  these  changes. 

Call  this  image  of  the  sun  the  solar  spectrum. 

Derive  the  term. 

Name  the  colors  of  the  spectrum,  beginning  at  the 
top. 

Inf.  1.    Which  rays  are  refracted  most? 

Inf.  2.    Which  rays  are  refracted  least  ? 

Write  a  topical  outline  of  the  lessons  on  light,  and 
a  connected  composition  upon  mirrors  or  refraction. 

PRACTICAL  QUESTIONS. 

1.  When    do  objects  extending  upward   from  the 
earth  cast  their  longest  shadows  in  the  sunlight  upon 
the  ground?     Why? 

2.  When  do  they  cast  their  shortest  shadows  ? 

3.  Upon  what  part  of  the  earth  are  the  shadows 
always  long? 

4.  When    and    where    do    such    objects    cast   no 
shadows  ? 

5.  What  part  of  the  moon  shines? 

6.  Does  it  shine  upon  the  earth  when  it  is  directly 
between  the  sun  and  the  earth? 


144  ELEMENTARY   LESSONS   IN   PHYSICS. 

7.  How  much  of  it  shines  upon  the  earth  at  any 
time? 

8.  Do  the  stars  shine  by  their  own  light,  or  by  the 
sun's  light  ? 

9.  Distinguish  between  a  planet  and  a  fixed  star. 

10.  Which  planets  do  you  know  ? 

11.  Does  the  earth  shine  ?     With  its  own  light  ? 

12.  How  can   the   sun  be  seen  before  it  has  risen 
above  the  horizon,   or  after  it  has  sunk   below   the 
horizon  ? 

13.  When  you  look  obliquely  into  clear  water,  why 
does  it  appear  shallower  than  it  is  ? 

14.  In  which  of  the  preceding  experiments  did  light 
from   the   object    actually    pass    through    the    points 
where  the  image  appeared  ? 

Call  an  image  so  formed  a  real  image. 

15.  In  which    experiments   did  no   light    from  the 
object  pass  through  the  points  where  the  image  ap- 
peared ? 

Call  such  an  image  a  virtual  image. 


CHEMISTRY  OF  AIR  AND  WATER  145 

XIV.    CHEMISTRY  OF  AIR  AND  WATER. 
THE  COMPOSITION   OF   THE  AIR 

EXPERIMENT   ISO      (At  school.) 

Into  a  shallow  pan  pour  enough  water  to  make  it 
about  1  inch  deep. 

Float  a  bit  of  red  phosphorus  as  large  as  a  good- 
sized  pea  upon  a  piece  of  cork  in  the  water. 

CAUTION.  —  Phosphorus  must  be  handled  with  tongs  or  forceps,  and 
not  touched  with  the  fingers.  It  should  be  cut  under  water,  and  when 
not  in  use  should  be  kept  under  water. 

Carefully  light  the  phosphorus  with  a  match  ;  and, 
holding  an  inverted  quart  jar  evenly,  lower  it  slowly 
over  the  phosphorus  until  it  rests  upon  the  bottom 
of  the  pan,  and  let  it  remain  there. 

Obs.  1.  Observe  carefully  all  that  takes  place  under 
the  jar. 

Describe  the  substance  formed  as  the  phosphorus 
burns. 

See  if  it  remains  under  the  jar. 

Inf.  1.   Where  must  it  have  gone  ? 

Phosphorus  is  an  element,  and  is  often  represented 
by  its  symbol  P. 

Inf.  2.  Could  the  cloudy  gas  have  consisted  of  P 
alone  ? 

Inf.  3.    What  could  have  combined  with  P  ? 

Inf.  4.    Why  did  the  water  rise  in  the  jar  ? 
10 


146  ELEMENTARY  LESSONS  IN  PHYSICS. 

Obs.  2.    Was  the  P  all  consumed  ? 

Inf.  5.   Why  did  n't  the  burning  continue  ? 

Obs.  3.  How  does  the  part  of  the  air  left  in  the 
jar  compare  in  volume  with  that  which  combined 
with  the  P? 

Call  the  part  of  the  air  which  combined  with  the  P 
Oxygen. 

Derive  the  terms  oxygen  and  phosphorus. 

Call  that  which  remains  in  the  jar  nitrogen.  It  is 
an  element,  symbol  N. 

Derive  the  term. 

Call  the  substance  formed  by  the  union  of  P  and 
0  phosphorus  pentoxide. 

Inf.  6.   Is  it  an  element  or  a  compound  ? 

Derive  the  name. 

Inf.  7.   Infer  what  proportion  of  the  air  is  0. 
Inf.  8.    Infer  what  proportion  of  the  air  is  N. 

PREPARATION  OF   OXYGEN. 

EXPERIMENT  181.     (At  school.) 

Powder  in  a  mortar  a  spoonful  of  thoroughly  dried 
potassium  chlorate. 

Mix  with  this  an  equal  quantity  of  manganese 
dioxide. 

Fill  a  large  hard-glass  test  tube  one  third  full  of 
this  mixture. 

Fit  a  stopper  into  the  mouth  of  the  test  tube. 

Perforate  the  stopper  and  fit  into  it  a  glass  tube 
about  16  inches  long,  bent  as  shown  in  the  figure. 


CHEMISTRY   OF    AIR   AND   WATER. 


147 


Cut  a  hole  1  inch  in  diameter  in  the  bottom 
and  near  the  rim  of  a  tin  plate  (P,  Figure  58)  5  or  6 
inches  in  diameter. 

Cut  another  hole  f  of  an  inch  in  diameter  just  be- 
low the  hem  in  the  rim  of  the  plate  and  above  the 
hole  in  the  bottom. 


Fig.  58.. 

Invert  this  plate  in  a  pan,  and  pour  into  the  pan 
enough  water  to  fill  it  a  little  above  the  bottom  of  the 
inverted  plate. 

Fill  four  horse-radish  bottles  with  water,  and,  cover- 
ing the  mouths  of  these  with  pieces  of  window  glass, 
invert  them,  filled  with  water,  upon  the  bottom  of 
the  plate  in  the  pan,  placing  one  of  them  over  the 
hole  in  the  bottom  of  the  plate,  and  removing  the 
pieces  of  window  glass. 

Support  the  test  tube  so  that  the  end  of  the  glass 
tube  will  reach  beneath  the  surface  of  the  water  in 
•the  pan. 


148  ELEMENTARY   LESSONS   IN   PHYSICS. 

Carefully  heat  the  test  tube  with  the  gas  or  alcohol- 
lamp  flame,  moving  the  flame  so  as  to  heat  the  part 
containing  the  mixture  evenly  throughout. 

As  soon  as  bubbles  begin  to  escape  rapidly  from  the 
tube,  insert  the  end  of  the  tube  through  the  hole  in 
the  rim  of  the  inverted  plate. 

When  one  bottle  is  filled  with  gas,  promptly  close 
the  mouth  of  it  by  slipping-  a  piece  of  window  glass 
under  it,  remove  this  bottle,  and  slip  another  over  the 
hole  in  the  pan. 

In  this  way  fill  all  the  bottles  with  the  gas. 

While  the  bottles  are  being  filled,  it  may  be  neces- 
sary to  dip  out  a  little  water,  from  the  pan,  to  prevent 
the  water  from  getting  too  high  and  floating  up  the 
bottles  of  gas. 

Take  the  delivery  tube  from  the  water  before  re- 
moving the  flame  from  the  test  tube.  (Why?) 

PROPERTIES  OF  OXYGEN. 

EXPERIMENT   188.      (At  school.) 

Light  a  splinter  of  pine  wood,  and  when  it  gets  to 
burning,  blow  out  the  flame  and  thrust  the  glowing 
coal  into  a  jar  of  oxygen,  keeping  the  jar  closed. 

06s.   Observe  the  effect. 

EXPERIMENT   183.      (At  school.) 

Wind  one  end  of  a  piece  of  wire  10  inches  long 
about  a  small  piece  of  charcoal,  ignite  the  charcoal, 
and  thrust  it  into  the  second  jar  of  oxygen. 


CHEMISTRY  OF   AIR  AND  WATER.  149 

Obs.    Observe  the  effect. 

The  charcoal  consists  chiefly  of  the  element  Cu,*- 
bon(C). 

EXPERIMENT  184.     (At  school.) 

Wind  one  end  of  a  piece  of  wire  10  inches  long 
about  a  piece  of  crayon,  as  shown  in  Figure  59. 

Hollow  out  the  top  of  the  crayon,  and,  place  a  piece 
of  roll  sulphur  (brimstone)  as  large  as  a  pea  in  the 
hollow. 


Fig.  59. 

Ignite  the  sulphur  and  lower  it  into  a  jar  of 
oxygen. 

Obs.   Observe  the  effect. 

EXPERIMENT   185.      (At  school.) 

Heat  one  end  of  a  piece  of  fine  iron  or  steel  wire, 
and  dip  it  into  powdered  sulphur,  so  as  to  melt  the 
sulphur  and  make  it  stick  to  the  wire. 


150  ELEMENTARY  LESSONS  IN  PHYSICS. 

Ignite  the  sulphur  on  the  end  of  the  wire,  and 
insert  it  in  a  jar  of  oxygen. 

Obs.    Observe  the  effect. 

Inf.  1.  What  do  these  experiments  show  about  the 
affinity  of  oxygen  for  other  elements  ?  - 

A  compound  of  oxygen  with  another  element  is 
called  an  oxide. 

Inf.  2.  What  different  oxides  have  been  formed  in 
these  experiments? 

Write  a  connected  description  of  oxygen,  —  its  pre- 
paration and  properties. 

The  rapid  union  of  oxygen  with  another  element 
accompanied  by  light  and  heat  is  called  combustion. 

Derive  the  name. 

COMBUSTION,  COMPOSITION   OF  WATER. 

A  candle  is  composed  chiefly  of  carbon  and  hy- 
drogen. 

EXPERIMENT  186.     (At  home.) 

Light  a  candle,  and  hold  a  cold  lamp  chimney 
over  it. 

Obs.   What  collects  on  the  chimney? 

Inf.  1.  What  is  one  substance  produced  in  the 
burning  of  the  candle? 

Inf.  2.  What  is  probably  one  of  the^  elements  of 
which  it  is  composed?  (Recall  definition  of  com- 
bustion.) 

Let  us  see  if  we  can  learn  what  the  other  part 
of  water  is. 


CHEMlbTRY   OF   AlK   AND   WATER.  151 


Fig  60. 
EXPERIMENT  187.     (At  school.) 

Fill  a  horse-radish  bottle  with  water,  and,  holding 
a  glass  plate  over  its  mouth,  invert  it,  and  place  it  in 
a  pan  containing  a  little  water. 

Wrap  a  piece  of  sodium  as  large  as  a  pea  in  a 
paper,  and,  holding  it  with  forceps,  place  it  quickly 
under  the  jar  without  raising  the  mouth  of  the  jar 
out  of  the  water. 

Obs.  1.   Observe  what  happens. 

Cover  the  mouth  of  the  jar,  and  place  it  upright 
upon  the  table'. 

Light  one  end  of  a  splinter  of  pine  wood  1  foot 
long  or  more,  slip  the  cover  aside,  and  thrust  the 
burning  end  of  the  splinter  quickly  into  the  lower 
part  of  the  bottle. 

Obs.  2.  Observe  what  happens  to  the  burning  stick, 
and  to  the  gas  in  the  bottle. 


152  ELEMENTARY   LESSONS  IN   PHYSICS. 

Obs.  3.  Notice  what  forms  on  the  inside  of  the 
bottle. 

Inf.  1.   This  water  was  formed  in  what  process? 

Inf.  2.    Then  it  was  formed  from  what  substances  ? 

Inf.  3.  From  what  substance  do  you  think  the  gas 
came?  Why? 

1.   Describe  the  gas. 

[How  does  it  differ  from  0  ?     (See  Obs.  2.)] 

It  is  hydrogen  (H). 

Derive  the  name.     (See  oxygen.) 

Inf.  4.   What  is  water  composed  of? 

Obs.  4.  When  a  lamp  or  gas  is  lighted  and  a  cold 
chimney  is  placed  over  the  flame,  what  gathers  on  the 
chimney  ? 

Inf.  5.  Where  do  the. elements  which  form  it  come 
from? 

Let  us  see  if  we  can  learn  whether  any  other  sub- 
stance than  water  is  formed  in  the  burning  of  the 
candle. 

EXPERIMENT  188.     (At  school., 

Fit  a  vaseline  bottle,  or  other  wide  mouthed  bottle, 
with  a  good  stopper. 

Into  this  stopper  fit  air-tight  two  glass  tubes,  one 
about  10  inches  long,  just  reaching  through  the  stop- 
per from  above,  and  the  other  long  enough  to  reach 
nearly  to  the  bottom  of  the  bottle  and  project  an  inch 
above  the  top  of  the  stopper. 

By  means  of  a  piece  of  rubber  tubing  6  or  8  inches 
long,  connect  the  top  of  this  last  tube  with  the  tube 
of  a  small  tin  tunnel 


CHEMISTRY  OF   AIR  AND  WATER.  153 

Fill  the  bottle  two  thirds  full  of  water. 

Obs.  1.  Placing  the  top  of  the  long  tube  in  the 
mouth,  draw  in  a  long  breath  from  the  bottle,  and 
observe  the  effect. 


Fig.  61. 

Inf.  What  is  the  gas  that  bubbles  up  through  the 
water  ?  Why  does  it  enter  the  bottle  ? 

Does  the  water  seem  to  be  affected  by  it  ? 

Hold  the  mouth  of  the  tunnel  a  little  above  a 
burning  candle,  and  draw  in  one  or  two  long  breaths 
as  before. 

Obs.  2.    Is  the  water  affected? 

EXPERIMENT  189.     (At  school.) 

Pour  out  the  water  from  the  bottle,  and  pour  in  as 
much  lime-water 


154  ELEMENTARY   LESSONS   IN   PHYSICS. 

'  Obs.  1.  Repeat  the  two  parts  of  the  last  experi- 
ment just  as  with  water,  and  notice  any  effect  upon 
the  lime-water. 

Obs.  2.  Let  the  bottle  stand  for  a  short  time,  ob- 
serve any  change  in  the  liquid,  and  notice  carefully 
the  bottom  of  the  bottle. 

Inf.  1.  Infer  what  the  coloring  of  the  liquid  was 
due  to. 

Inf.  2.  Infer  how  many  substances  must  have 
combined  to  form  this  new  substance. 

Inf.  3.    Infer  where  they  must  have  come  from. 

Inf.  4.  Could  that  which  came  from  the  burning 
candle  have  been  the  water  ? 

Why  not? 

Inf.  5.    What  state  of  matter  was  it  ? 

We  will  prepare  some  of  it  in  another  way. 

EXPERIMENT   19O.      (At  school.) 

Prepare  a  horse-radish  bottle  of  0,  and,  keeping  the 
jar  closed  as  much  as  possible,  repeat  Experiment 
183. 

Inf.  1.  Is  the  substance  left  in  the  jar  0?  How 
do  you  know  ? 

Inf.  2.   What  was  it  formed  from? 

Inf.  3.  Infer  what  element  combined  with  the 
oxygen. 

The  gas  formed  is  called  carbon  dioxide. 

EXPERIMENT   191.      (At  school.) 

Obs.  Thrust  a  lighted  match  into  the  jar  in  which 
the  charcoal  was  burned,  and  observe  the  effect 


CHEMISTRY  OF  AIR  AND  WATER.  155 

EXPERIMENT  199.     (At  school.) 

Obs.  Lower  a  lighted  candle  into  the  jar,  and  ob- 
serve the  effect. 

In  these  experiments  keep  the  jar  closed  as  much  as  possible. 

EXPERIMENT   193.     (At  school.) 

Obs.  Pour  a  little  lime-water  into  the  jar,  shake 
it,  and  observe  the  effect. 

Inf.  1.  Infer  what  the  substance  was  which  came 
from  the  burning  candle  and  acted  upon  the  lime- 
water. 

Inf.  2.  What  two  substances  are  formed  in  the 
burning  of  a  candle  ? 

Supplementary  experiments  may  be  taken  to  see  if 
carbon  dioxide  is  formed  in  the  burning  of  kerosene, 
illuminating  gas,  and  wood. 

CHANGES  IN  AIE  IN  THE  HUMAN  BODY. 

EXPERIMENT  194.      (At  home.) 

Obs.  Breathe  upon  a  cool  piece  of  glass  or  china, 
and  observe  the  effect. 

Inf.   Infer  one  substance  given  out  in  breathing. 

EXPERIMENT  195.     (At  school  ) 

Obs.  Refill  with  lime-water  the  bottle  used  in  Ex- 
periments 188-9,  remove  the  short  glass  tube  from  the 
stopper,  push  the  other  tube  through  the  stopper  far 
enough  to  reach  nearly  to  the  bottom  of  the  bottle, 
breathe  out  through  the  glass  tube,  and  observe  th« 
effect  upon  the  lime-water. 


156  ELEMENTARY  LESSONS  IN   PHYSICS. 

Inf.  1.  Infer  another  substance  given  out  in  breath- 
ing. 

1.  Compare  the  substances  given  out  in  breathing 

with   those    formed    in   the   burning   of   the 
candle. 

2.  What   substance   is    taken    out    of    the    air   in 

combustion  ? 

Inf.  2.  Infer  what  is  taken  from  the  air  in  the  act 
of  breathing. 

Inf.  3.  What  objections  are  there  to  breathing  the 
same  air  over  and  over? 

///.  4.  Does  a  lighted  lamp  or  gas  jet  improve,  or 
injure  the  air  of  a  room  for  breathing? 

Three  men  had  occupied  the  closed  cabin  of  a  boat 
for  an  hour,  when  it  was  found  that  a  match  would 
not  burn  in  the  cabin. 

Inf.  5.    Infer  why. 

Inf.  6.   Was  such  air  fit  to  breathe? 

Inf.  7.  What  must  be  done  with  the  air  of  an 
occupied  room  to  keep  it  fit  for  breathing? 

Describe  fully  in  writing,  with  drawings  of  appara- 
tus, experiments  showing  changes  in  the  burning 
candle  and  in  the  human  body. 

Is  your  school-house  properly  ventilated  ? 

If  so,  write  a  description  of  the  system,  with  dia- 
grams. 

If  not,  think  out  a  good  plan  for  ventilating  it,  and 
present  it  in  writing,  with  diagrams. 


PREFIXES   AND   SUFFIXES 

OCCURRING  IN  WORDS  TO  BE  DERIVED  IN  THIS  STUDY. 


LATIN  PREFIXES. 
ad-     f=     to 

-able 

LATIN  SUFFIXES. 
=     that  may  be. 

at-      > 

-al 

) 

con-    ) 

-ar 

y  =     relating  to,  like. 

/ 

\ 

com-  -  =     teiti,  Hooker. 

CO. 

cor-    ; 

-ary 
-ant 
-ent 

) 
)  f  that  which  (in  nouns). 
>        i  same  as  -ing  (in  adjs.). 

de-        =     down,  off. 
dif-     > 

-ance 
-ence 

1  =     condition,  quality. 

>•  =    apart. 
di-      > 

-or 

=    that  which. 

ex-     )_     Qut 

-fie 

=    making. 

e-       ) 

-ian 

=     belonging  to. 

in-      ? 

im-     >•  =     not,  into,  on. 
il-       ) 

-ion 
-id 
-ism 

=    act  of,  quality  of,  result  of. 
=     like,  relating  to. 

[•  =     quality. 

noil-     =     not. 

-ity 

> 

pen-      =    almost. 

-ive 

=1     having  the  power  of. 

re-         =     ftacfc,  again. 

-men  t 

=     condition. 

sub-      =     under,  after. 

-ous 

=     abounding  in. 

(  across, 

-ule 

I  =     minute. 

trans-  =  <  beyond, 

-ulum 

\ 

(  through. 

GREEK  PREFIXES. 

GREEK  SUFFIXES. 

a-           =     not,  without. 

-ide 

=     composed  of. 

di-         =     two. 

-ize 

=    make,  render. 

pent-    =    five. 

ANGLO-SAXOX  PREFIX. 
mi-        =    not. 


APPARATUS   AND   MATERIALS. 

The  quantities  of  materials  indicated  in  many  cases  will  be  sufficient  for 
performing  the  experiment  a  number  of  times.  Gas  or  alcohol  lamp  will  be 
needed  in  many  experiments,  and  will  not  be  mentioned  each  time.  If  de- 
sired, apparatus  may  be  ordered  from  the  Publishers,  THOMPSON,  BROWN  &  Co., 
Boston. 

I.    NATURE  OF  MATTER. 
Exp.  1.    Narrow  mouth  bottle.     Exp.  2.   Tumbler  and  tin  pan. 

II.    DIVISIONS  OF  MATTER. 

Exp.  3.  Lump  of  salt,  mortar,  \  oz.  metallic  sodium,  small  package 
bleaching  powder,  1  Ib.  commercial  sulphuric  acid,  and  a  test  tube. 
Exp.  4.  Tumbler  and  £  oz.  bottle  of  "bluing." 

III.    STATES  OF  MATTER. 

Exp.  5.  Tumbler.  Exp.  6.  Small  stick  of  sealing  wax,  string,  and  3  or 
4  oz.  weight.  Exp.  7.  2  wide  mouth  1  oz.  bottles,  2  rubber  stoppers  to 
fit  (1  with  1  hole  and  1  with  2  holes),  3  pieces  glass  tubing  (2",  3",  and 
6"  long),  1'  rubber  tubing,  and  a  few  drops  of  red  ink.  Exp.  8.  Test  tube, 
test  tube  holder,  and  alcohol  lamp  or  gas. 

IV.    CHANGES  IN  MATTER. 
Exp.  9.    Test  tube,  bit  of  copper,  and  2  oz.  nitric  acid. 

V.    FORCE. 

Exp.  10.  Chair.  Exp.  11.  Pail  or  pan,  and  chips  of  wood.  Exps.  12, 
13.  Brick  or  stone.  Exp.  16.  Wax  and  match.  Exp.  17.  &  oz.  solution 
of  silver  nitrate.  Exp.  18.  Magnet  and  bits  of  copper,  iron,  lead,  zinc, 


APPARATUS  AND   MATERIALS. 

silver,  steel,  and  wood.  Exp.  19.  \  yd.  silk  cloth  and  straight  lamp 
chimney.  Exp.  20.  Tumbler,  sulphuric  acid,  zinc  and  copper  plates  and 
connecting  wires,  \  Ib.  potassium  bichromate,  and  a  wire  magnet.  Exp. 
21.  A  cent.  Exp.  22.  A  match.  Exp.  23.  Tumbler,  \  Ib.  powdered 
alum,  and  thread.  Exp.  24.  Plate  or  pan,  and  2  glass  plates  3"  X  3". 
Exp.  25.  Glass  tubes  3"  long  of  different  six.es.  Exp.  26.  Ammonia,  test 
tube,  small  wide  mouth  bottle,  j  Ib.  powdered  charcoal,  and  filter  paper, 
4"  diameter.  Exp.  27.  Ball.  Exp.  28.  Marble.  Exp.  29.  Larger  mar- 
ble. (Exps.  28,  29,  need  not  be  actually  performed.)  Exp.  30.  Fan. 
Exps.  31-33.  Large  book  and  string.  Exp.  34.  Same  and  64  oz.  spring 
balance.  Exp.  35.  Spring  balance  and  3  tin  cans,  —  pint,  quart,  and 
2-quart.  Exps.  36-38.  Set  of  lead  weight,  —  2  of  1  unit,  2  of  2  units, 
and  2  of  3  units,  —  mechanical  power  frame  with  2  pulleys  fixed  1'  apart, 
string,  pins,  foot  ruler  with  tack  in  each  end  (in  place  of  bar  Fig.  11),  and 
strong  manilla  envelope. 

VI.     GRAVITY. 

Exps.  39,  40.  Sheet  of  stiff  card-board  about  7"  X  10",  strong  thread 
and  weight,  and  pins.  Exps.  41-46.  Thread  and  2  weights, —  1  unit  and 
3  units.  Exp.  47.  Old  clock.  Exps.  48,  49.  Gem  lamp  chimney,  sheet 
rubber  (3^"  X  3^"),  rubber  stopper  (1  hole)  to  fit  small  end  of  chimney, 
3"  glass  tubing,  2'  rubber  tubing,  and  glass  funnel.  Exp.  50.  Same  and 
rubber  (or  rubber  bound)  stopper  to  fit  large  end  of  chimney,  fitted  with 
jet  tube.  Exp.  51.  Same  and  2'  glass  tubing,  spirit  level.  Exp.  52.  Tin 
can  (pint  or  larger)  with  overflow,  catch-bucket,  or  tumbler  with  string 
bail,  and  4  Ib.  spring  balance.  Exp.  53.  Spring  balance  and  4  oz.  (or 
larger)  narrow  mouth  bottle.  Exp.  54.  T.  D.  clay  pipe,  sheet  rubber 
(3"  X  3"),  and  strong  thread.  Exp.  55.  Tumbler  and  thin  card-board 
3"  X  3".  Exp.  56.  Small  glass  tube.  Exp.  57.  Pan  and  tumbler.  Exp. 
58,  59.  Barometer  tube,  5"  strong  rubber  tubing,  strong  thread,  and  1  Ib. 
mercury.  Exp.  60.  Glass  tube  6"  long  and  about  f"  bore,  with  piston  to 
fit.  Exp.  61.  Lifting  pump.  Exp.  62.  Force  pump. 

VII.     SIMPLE  MACHINES. 

Exps.  65-67.  Mechanical  power  frame,  lever,  and  set  of  weights  (2  of 
1  unit,  2  of  2  units,  and  2  of  3  units).  Exps.  68,  69.  Wheel  and  axle. 
Exps.  70-73.  Set  of  pulleys  (3  fixed  and  1  movable)  and  cord  (3'),  with 
hooks  at  ends.  Exps.  74,  75.  Inclined  plane  and  car,  jack-screw,  or 
bench-screw. 


1586  ELEMENTARY  LESSONS  IN  PHYSICS. 


VIII.    HEAT. 

Exp.  77.  Cent.  Exp.  78.  Nail,  hammer,  and  anvil.  Exp.  79.  Marble 
and  wire  ring,  and  alcohol  lamp  or  gas.  Exp.  80.  Test  tube  fitted  with 
rubber  stopper  (1  hole),  and  6"  glass  tube.  Exp.  81.  Common  thermome- 
ter. Exp.  82.  Same  as  for  exp.  80.  Exp.  83.  Tin  can,  ice,  and  support 
for  can.  Exp.  84.  Iron  spoon  and  bit  of  lead.  Exp.  85.  Tin  can,  ice, 
salt,  and  small  test  tube.  Exp.  86.  Large  test  tube  and  test  tube  holder. 
Exp.  87.  Tin  pan  arid  support.  Exp.  88.  Thin  watch  crystal  and  little 
ether.  Exp.  89.  Same  as  for  exp.  86  and  cold  glass.  Exp.  90.  Ther- 
mometer, tin  can,  and  ice.  Exp.  94.  6"  iron  rod  and  wire  support, 
2  marbles,  and  wax.  Exp.  95.  Same  as  for  exp.  94  and  slate  pencil. 
Exp.  96.  Several  kinds  of  wood,  iron,  cotton  cloth,  woollen  cloth,  silk,  and 
thermometer.  Exp.  97.  Test  tube.  Exp.  98.  Tin  can  (small  mouth) 
and  scales  or  spring  balance.  Exp.  99.  Tin  pan  and  support,  and  saw- 
dust. Exp.  100.  Apparatus  shown  in  Fig.  37.  Exp.  101.  Lamp-with 
large  chimney  and  tissue  paper.  Exp.  102.  Oil  stove  and  thin  paper. 
Exps.  104,  105.  Small  flask  and  support,  chemical  thermometer,  tin  can, 
perforated  stopper  to  fit  flask,  and  16"  glass  tubing  bent  as  shown  in  Fig. 
39.  Exp.  106.  2  test  tubes,  fine  ice  or  snow,  can  of  hot  water. 

IX.    MAGNETISM. 

Exps.  107-113.  2  magnets  (bar  and  horseshoe),  wire  nail,  iron  filings, 
6"  steel  wire,  and  silk  thread. 

X.    FRICTIONAL  ELECTRICITY. 

Exp.  114.  Silk  ribbon  and  J  yd.  flannel.  Exp.  115.  Large  rubber 
eraser  and  £  yd.  silk.  Exps.  116-122.  Large  stick  sealing  wax  and 
flannel,  pith-ball  and  balanced-bar  electroscopes,  lamp  chimney,  and  silk. 
Exp.  123.  2  lamp  chimneys  and  silk  rubbers,  2  sticks  sealing  wax  and 
flannel  rubbers,  12"  wire  bent  as  in  Fig.  45,  and  silk  thread.  Exps.  124- 
127.  Chimney,  sealing  wax,  and  rubbers,  balanced  bar,  tumbler,  1'  glass 
tubing,  maple  rule,  and  baking  powder  can  and  cover. 

XI.     VOLTAIC  ELECTRICITY. 

Exp.  128.  Same  as  for  exp.  20.  Exp.  129.  Same  and  30'  insulated  no. 
22  copper  wire  or  helix,  6"  iron  rod,  and  tacks.  Exp.  130.  Grenet  battery 
(1  (±t.)  and  3"  fine  platinum  wire. 


APPARATUS  AND  MATERIALS.  158c 


XI L     SOUND. 

Exp.  131.  Pitchfork  (maybe  borrowed).  Exp.  133.  Call  ball.  Exp. 
134.  Lath  or  yard  stick,  and  tuning  fork.  Exp.  135.  Tin  spice  box  and 
cover,  and  12'  of  string.  Exp.  136.  Tumbler.  Exps.  137-142.  Sonome- 
ter. Exps.  143,  144.  Organ  pipe  with  glass  side  and  membrane,  and  18" 
rubber  tubing.  Exps.  145-147.  2  narrow  mouth  bottles  (1  oz.  and  4  oz.). 
Exp.  148.  Organ  pipe.  ' 

XIII.     LIGHT. 

Exps.  149-153.  Porte  lumiere,  piece  of  window  glass,  piece  of  colored 
glass,  and  double  convex  lens.  Exp.  154.  Soap  box,  tinfoil  2"  X  2", 
and  candle.  Exp.  155.  Darkened  room.  Exp.  156.  Lamp  (giving  broad 
flame)  and  small  cube  or  sphere  (|"  or  f).  Exps.  157-160.  Porte  lu- 
miere and  plane  mirror  turning  on  a  horizontal  axis.  Exps.  161,  162. 
2  plane  mirrors  set  parallel  and  at  angles  (Fig.  53).  •  Exps.  163-167.  Porte 
lumiere,  convex  mirror,  candle,  and  screen.  '  Exps.  168,  169.  Porte  lu- 
miere, plane  mirror  on  axis,  glass  tank  (Fig.  54),  and  red  ink.  Exp.  170. 
Tin  pan  and  cent.  Exps.  171-177.  Porte  lumiere,  2  double  convex  lenses 
(one  with  greater  focal  distance  than  the  other),  yard  stick  and  supports, 
2  lens  holders,  lamp  or  candle  and  support  for  same,  and  screen  (all  sliding 
on  yard  stick).  Exps.  178,  179.  Glass  prism. 


XIV.     CHEMISTRY  OF  AIR  AND  WATER. 

Exp.  180.  Tin  pan,  flat  cork,  bit  of  red  phosphorus,  and  quart  glass  jar. 
Exps.  181-185.  Same  and  mortar,  £  Ib.  potassium  chlorate,  |  Ib.  manga- 
nese dioxide,  $"  test  tube,  perforated  stopper,  16"  glass  tube,  5"  tin  plate 
(P.,  Fig.  58),  and  4  wide  mouth  bottles  (4  oz.  or  larger),  2  pieces  nos.  18- 
20  iron  wire  about  12"  long,  bit  of  charcoal,  roll  sulphur,  and  2  fine  iron 
wire.  Exp.  186.  Candle  and  lamp  chimney.  Exp.  187.  Tin  pan,  wide 
mouth  bottle,  metallic  sodium,  and  forceps.  Exps.  188,  189.  Wide  mouth 
oz.  bottle,  rubber  stopper  to  fit  (2  holes),  glass  tubing  3"  and  6",  small 
tin  funnel,  5"  rubber  tubing,  and  lime  water.  Exps.  190-193.  Jar  of 
oxygen,  bit  of  charcoal  and  wire,  candle,  and  lime  water.  Exp.  194. 
Piece  of  cold  glass  or  china.  Exp.  195.  Apparatus  used  in  exps.  188, 
189. 


INDEX. 


NUMBERS  REFER  TO  PAGES. 


ABSORPTION  OF  GASES,  29. 

Action,  36. 

Adhesion,  19. 

Aeriform  matter,  11. 

Air-chamber,  69. 

Angle  of  incidence,  133. 

Angle  of  reflection,  133. 

Artesian  wells,  57. 

Atom,  6. 

Attraction,    capillary,    29;   molar,   18 

molecular,  19,  26. 
Axle,  74. 

BALANCED  BAR,  109. 
Barometer,  63. 
Beam  of  light,  130. 
Boiling,  91. 

CAPILLARY  ATTRACTION,  29. 
Carbon  dioxide,  154. 
Centre  of  curvature,  136. 
Centre  of  gravity,  46. 
Centrifugal  force,  18. 
Changes  in  air, — 

In  combustion,  150. 

In  the  human  body,  155. 
Chemical  affinity,  16. 
Chemical  change,  14. 
Chemical  force,  16. 
Chlorine,  5. 
Clouds,  94. 
Cohesion,  19. 
Combustion,  150. 
Components,  41. 


Composition  of  forces,  39. 

Compound,  6. 

Compound  microscope,  141. 

Concave  mirror,  136. 

Condensation  of  vapor,  93. 

Conduction,  of  electricity,  111;  of  heat, 

95. 

Conductor,  of  electricity,  1 1 2 ,  of  heat,  95- 
Constant  force,  30. 
Convection  of  heat,  97. 
Correlation  of  forces,  26. 
Crow  bar,  74. 
Crystallization,  28. 
Crystals,  28. 

DEODORIZER,  30. 
Derivation,  2. 
Dew,  93. 
Dew  point,  94. 
Diffused  light,  134. 
Double  convex  lens,  139. 
Draught,  99. 

ECLIPSE  OF  MOON,  132. 

Eclipse  of  sun,  132. 

Effects  of  heat,  88 ;  of  Voltaic  electri- 
city, 114. 

Electro-magnet,  116. 

Electroscopes,  108. 

Element,  6. 

Energy,  39. 

Equilibrium,  40,  46. 

Evaporation,  92. 

Expansion,  of  gases,  90;  of  liquids,  38; 
of  solids,  88. 


160 


INDEX. 


FALLING  BODIES,  49. 

Filter,  29. 

Filtrate,  29. 

Fixed  pulley,  78. 

Floating  and  sinking,  59. 

Focal  distance,  136. 

Foot-pound,  38. 

Force,  16;  centrifugal,  18;  chemical, 
16 ;  constant,  30 ;  impulsive,  30 ;  meas- 
ure of,  37  ;  molar,  30 ;  muscular,  1 6 ; 
physical,  16  ;  tendency  of,  31. 

Force  pumps,  68. 

Frictioual  electricity,  21,  107. 

Frost,  94. 

Fulcrum,  71. 

GAS.  13 

Gravitation,  17. 
Gravity,  18,  45. 

HAIL,  94. 

Heat,   20;   conduction  of,   95;   effects 

of,  88;  latent,  101  ;  radiation  of,  94  ; 

sources  of,  87. 
Horse-power,  39. 
Hot- water  heating,  98. 
Hydrogen,  152. 

ILLUMINATED  BODIES,  126. 
Image,  — 

By  concave  mirror,  136. 

By  double  convex  lens,  140. 

By  plane  mirrors,  134. 

By  small  aperture,  131. 
Impenetrability,  4. 
Impulsive  force,  30. 
Inclined  plane,  82. 
Induction  of  electricity,  113. 
Inertia,  34. 
Inference,  2. 
Insulator,  112. 

LATENT  HEAT,  101. 
Law,— 

Of  magnets,  105. 

Of  electrical  action,  110. 

Of  reflection  of  light,  133. 


Lever,  71. 

Lifting  pumps,  65. 

Light,  20,  126. 

Line  of  direction,  46. 

Liquefaction,  90. 

Liquids,  8. 

Load  of  lever,  72. 

Loudness  of  tones,  120. 

Luminous  bodies,  126. 

Luminous  effects  of  electricity,  1 1 6 

MAGNETIC  DECLINATION,  106. 

Magnetic  effects  of  electricity,  116. 

Magnetic  needle,  105. 

Magnetism,  21,  103. 

Magnets,  103. 

Mass,  6. 

Matter,  1. 

Measure  of  atmospheric  pressure,  64 

Measure  of  force,  37 

Medium,  129. 

Microscopes,  141. 

Mirrors,  134. 

Molecular  attraction,  19,  26. 

Molecule,  5,  7. 

Momentum,  33. 

Movable  pulley,  78. 

Muscular  force,  16. 

NEGATIVE  ELECTRICITY,  110. 
Negative  pole,  105. 
Neutral  equilibrium,  47. 
Nitrogen,  146. 
Non-luminous  bodies,  126. 

OBSERVATION,  1. 
Odor,  7. 

Opaque  bodies,  129. 
Organ  pipe,  123. 
Oxide,  149. 
Oxygen,  146. 

PENCIL  OF  LIGHT,  130. 
Pendulum,  49. 
Penumbra,  132 
Permanent  magnet,  104. 
Phosphorus,  145. 


INDEX. 


161 


Phosphorus  pentoxide,  146. 
Physical  change,  15. 
Physical  force,  16. 
Physics,  15. 
Pitch  of  tones,  121. 
Pith-ball  electroscope,  108. 
Poles  of  a  magnet,  105. 
Porte  luiniere,  126. 
Positive  electricity,  110. 
Positive  pole,  105. 
Power,  38. 
Power  of  lever,  72. 
Preparation  of  oxygen,  146. 
Pressure  of  air,  62. 
Pressure  of  liquids,  52. 
Principal  focus,  136,  140. 
Pulleys,  78. 
Pumps,  65 

RADIATIOX,  94. 

Radiator,  95. 

Rain,  94. 

Ray  of  light,  130. 

Reaction,  36. 

Reflection  of  light,  133. 

Refraction  of  light,  137. 

Resistance  of  air,  35;   of  friction,  35; 

of  gravity,  36 ;  of  inertia,  35. 
Resultant,  41. 

SCREW,  83. 

Shadow,  132. 

Simple  machines,  71. 

Snow,  94. 

Sodium,  5. 

Solar  spectrum,  143. 

Solidification,  90. 

Solids,  9. 

Solution,  27. 

Sonometer,  121. 

Sound,  how  produced,  117. 

Sources  of  heat,  87 ;  of  light,  126. 


Specific  gravity,  59. 
Spirit  level,  55. 
Springs  and  wells,  55. 
Stable  equilibrium,  47. 
Steam  heating,  102. 
Steelyard,  74. 
Substance,  4. 

Surface  of   liquids   in  communicating 
vessels,  54. 

TELESCOPE,  142. 
Temporary  magnet,  103. 
Terrestrial  magnetism,  105. 
Thermal  effects  of  electricity,  116. 
Thermometer,  89. 
Transfer  of  heat,  94. 
Translucent  media,  129. 
Transmission  of  light,  129. 
Transmission  of  sound,  118. 
Transparent  media,  129. 

UMBRA,  132. 

Unstable  equilibrium,  47. 

VAPOR,  13. 

Vaporization,  92. 

Velocity,  32 ;  of  light,  133 ;  of  sound, 

119. 

Vibrating  columns  of  air,  124. 
Vibrating  strings,  120. 
Vibrations  of  the  pendulum,  50. 
Vibrations,  transmission  of  sound,  118. 
Voltaic  electricity,  21,  114. 
Voltaic  element,  114. 

WATER,  composition  of,  150. 

Water  as  a  conductor  of  heat,  96. 

Waterworks,  55. 

Wedge,  85. 

Wheel  and  axle,  74. 

Winds,  100. 

Work,  38. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

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This  book  is  DUE  on  the  last  date  stamped  below. 


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